NCERT Solutions: Tenths and Hundredths

Page no. 134

1. What was the length of the smallest pencil you have used?

Ans: The length of the smallest pencil I have used is 2 cm.

2. How long is this pencil? Guess _______ cm

Ans: I guess the pencil is 3 cm long.

3. Measure it using a scale. How good is your guess?

Ans: It is more than 3 cm and less than 4 cm. So my guess was close.

4. What is the length of this pencil? _______ mm. What is its length in centimetres?

Ans: The length of the given pencil is 6 mm, and its length in centimeters is six-tenths of a centimetre, i.e., 0.6 cm.

Frogs

5. Have you seen frogs? Where? How many different types of frogs have you seen? Are all the frogs of the same length? 

Ans: Yes, I have seen frogs in ponds, lakes, etc. I have seen many kinds of frogs.

No, not all  frogs are the same length.

Here are two interesting examples.

6. What does 0.9 cm mean? It is the same as _____ millimetres. We can also say this is nine-tenths of a cm. Right?

Ans: Yes, you're correct!

0.9 cm is the same as 9 millimeters.

To convert centimeters to millimeters, we multiply by 10 (since there are 10 millimeters in 1 centimeter). So:

0.9 cm×10=9 mm

We can also say that 0.9 cm is indeed nine-tenths of a centimeter.

 7. So 30.5 cm is the same as ____ cm and ____ millimetre.

Ans: So, 30.5 cm is the same as 30 cm and 5 millimeters. (since 1 cm = 10 millimeters)

8. About how many of the big frogs will fit on the 1m scale? ______

Ans:  We have 1 m = 100 cm. 

The length of the big frog is 30.5 cm. 

Thus, 3 big frogs will fit on the 1 m scale (because 30.5 × 3 = 91.5 which is close but less than 100 cm).

9. If they sit in a straight line about how many of the small frogs will cover 1m? _______

Ans: 1 m = 100 cm. 

The length of small frog = 9 cm. 

Thus, 11 frogs can cover the length of 1 m (because 9 × 11 = 99 which is close but less than 100 cm).

Page no. 135

Practice time 

1. Length of the nail _____ Cm and ______ Mm or ______ Cm.     

Ans: Length of the nail is 2 cm and 9 mm or 2.9 cm.

 2. The length of this lady's finger (bhindi) is ______cm and ______mm. 

We can also write it as  ____ cm.

Ans: The length of this lady's finger is 8 cm and 3 mm. We can also write it as 8.3 cm.

 3. Using the scale on this page find the difference in length between candle 1 and candle 3? 

Ans:  

Candle 3: 6 cm

Candle 1: 2.9 cm

Difference between candle 1 and candle 3 = 6 cm - 2.9 cm = 3.1 cm

So, the difference in length between Candle 1 and Candle 3 is 3.1 cm.

Page no. 136

4. Guess and Colour

Ans:  

5. Guess, Draw and Measure

Ans:

6. Our Eyes Get Confused? 

(i) Which line is longer? A or B? Measure each line and writes how long it is in centimetres. How good is your guess?

Ans:  I think line B is longer than A. On Measuring: line (A) = 4.6 cm and Line (B) = 4.6 cm.

Both lines are equal. My guess is incorrect.

 (ii)  Which line is longer? C or D? Measure each line. How good is your guess?

Ans:  Line (C) appears to be longer than the line (D). On measuring: Line (C) = 3.2 cm and Line (D) = 3.2 cm. 

Both lines are equal. My guess is incorrect.

7. Whose Tail is the Longest?

Guess whose tail is the longest. Now measure the tails. How good is your guess?

Ans:

8. The Longest Rupee Notes?

(i) What is the length of a 100 rupee note? Guess. Now measure it using a scale.

Ans: 

(ii)  Now guess the length and width of many other things. Measure and find the difference between your measure and your guess.

Ans:

Here, the difference between measurement and guess is

9. At the Market

(i) How many paise does a matchbox cost?

Ans: A matchbox costs 50 paise.

 (ii) How many match-box can be got for Rs. 2.50?

Ans: Five matchboxes can be bought for Rs. 2.50.

 (iii) How many rupees does the soap cost?

Ans: A soap costs Rs. 8.75.

 (iv) Arun wanted to buy a soap. He has a five-rupees coin. 2 one-rupee coins and 4 half-rupee coin. Write in rupees what money he will get back?

Ans: Total money with Arun = 1 x Rs. 5 + 2 x Rs 1 + 4 x Rs. 0.50

 = Rs. 5 + Rs. 2 + Rs. 2 = Rs. 9

Cost of a soap = Rs. 8.75

Arun will get back = Rs. 9 - Rs. 8.75

= 900 paise - 875 paise

= 25 paise = Re 0.25

 (v)  (a) An egg costs two and a half rupees. How much will one and a half dozen cost?

Ans:  One dozen =12 pieces

One and a half dozen = (12+6) = 18 pieces

Cost of one egg = Rs. 2.50

Cost of 18 eggs = Rs. (18 x 2.50)

= Rs. 18 x 2 + Rs. 18 x 0.50

= Rs. 36 + Rs. 9 = Rs. 45

 (b) How many pens can Kannan buy? How much money is left?

Ans: Money left after purchase of one and a half dozen eggs

 = Total money - Money spent

= Rs. 60 - Rs. 45

= Rs. 15

Cost of a pen = Rs. 6.50

 1 pen costs Rs. 6.50, so 2 pens cost Rs. 13.

3 x Rs. 6.50 = Rs. 19.50

Kannan can buy 2 pens

Money left with Kannan = Rs. 15- Rs. 13 = Rs. 2

 (vi) The price of two pens is Rs _______ Can she buy two pens?

Ans: Price of 1 pen = Rs. 6.50

Price of 2 pens = Rs. (2 x6.50) = Rs. 13

So, she can buy 2 pens with Rs. 13.

Page no. 140

Practice time - Match these

1.  Match each yellow box with one green and one pink box.

Ans: 

2. Colourful Design:

(i) What part of this sheet is coloured blue?

Ans:  1/10 part of the given sheet is coloured blue.

 (ii) Which part of the sheet is green?

Ans:  3/10 part of the given sheet is green.

 (iii) Which colour covers 0.2 of the sheet?

Ans: Black colour covers 0.2 of the given sheet.

(iv)  Now look at the second sheet. Each strip is divided into 10 equal boxes. How many boxes are there in all?

Ans: There are 10 × 10 = 100 boxes.

(v) Is each box  part of the sheet?

Ans: Yes, each box is part of the sheet.

 (vi) How many blue boxes are there?

Ans: There are 10 blue boxes.

 (vii) Is blue equal to  of the sheet? We saw that blue is also equal to of the sheet. We wrote it as 0.1 of the sheet.

Ans: Yes, blue boxes are equal to of the sheet.

 (viii) Can we say 10/100 = 1/10 = 0.10 = 0.1 ?

Ans: Yes, we can say 10/100=1/10 = 0.10 = 0.1.

Think: Can we write ten paise is 0.1 of a rupee?

Ans: Yes, we can write ten paise as 0.1 of a rupee.

(ix) How many boxes are red? What part of the sheet is this?  

Can we also write it as 0.15 of the sheet?

Ans: There are 15 red boxes. They are  part of the sheet.

It can also be written as 0.15 of the sheet.

 (x) Now  of the sheet is black. We can say 0. ....... Is black.

Ans: Now of the sheet is black. We can say 0.03 sheet is black.

 (xi) How many white boxes are there in the sheet?

Ans: There are 22 white boxes in the sheet.

 (xii) What part of the second sheet is white?

Ans: 22/100  part of the second sheet is white.

(xiii) Make your designs.

Ans:

3. Sports Day 

The school at Malappuram has its sports day. The first five children in the Long Jump are:

(i) Teena jumped 3.50m which is 3m and 50 cm. But how far did Anu jump? ____ m  and ____ cm.

Ans: Anu jumped 3m and 5 cm.

(ii) Who is the winner in the long jump?

Ans:  Rehana is the winner in the long jump.

 (iii) Write the names of the I , II and III winners on this stand.

Ans.  I is Rehana, II is Meena and III is Teena.

We can also write 1 cm as 0.01 m.

Page no. 142

4. Write in Metres

 Ans: 3 metre 45 centimetre = 3.45 m

    99 centimetre = 0.99 m

 1 metre and 5 centimetre = 1.05 m 

5. How Big Can You Get

Ans: Difference in size = 1.82 - 1.52 = 0.30 m

Ans: It is given that 

           = 2m - 45 m 

           We can write it as 

           = 200 cm - 45 cm 

            On further calculation, 

            = 155 cm

Page no. 143

 Practice Time

1.  Currency from different countries.

(i) Have you seen any notes or coins used in any other country? 

Ans: Yes, I have seen notes and coins used in Australia.

(ii) Shivam Bank has a chart to show us how many Indian rupees we can get when we change the money of different countries.

(A) The money of which country will cost the most in Indian Rupees?

 Ans: England's money will cost the most in Indian Rupees.

 (B) Mithun's uncle in America had sent him 10 USA dollars as a gift. Mithun used 350 rupees for a school trip. How much money was left with him?

Ans: Money received by Mithun = 10 USA Dollars

= 10 x Rs. 39.70

= 10 x Rs. 39 + 10 x 70 paise

= Rs. 390 + 700 paise

= Rs. 390 + Rs. 7

Money spent on school trip =Rs. 350

Money left with Mithun = Rs. 397- Rs. 350 = Rs. 47

 (C) Majeed's father is working in Saudi Arabia. He gets 1000, Saudi Riyal as salary. Arun's father who is working in Sri Lanka gets 2000 Sri Lankan Rupees. Who gets more Indian Rupees.

Ans: Majeed's father salary = 1000 Saudi Riyal

= 1000 x Rs. 10.52

= 1000 x Rs. 10 + 1000 x 52 paise

= Rs. 10000 + 52000 paise

= Rs. 10000 + Rs. 520 = Rs. 10520

Arun's father salary = 2000 Sri Lankan Rupees

= 2000 x Rs. 0.37

= 2000 x 37 paise

= 74000 paise = Rs. 740

 (D) Leena's aunty brought a present for her from China. It cost 30 Yuan. Find what it costs in Indian rupees.

Ans. Cost of the present = 30 Yuan

= 30 x Rs. 5.50

= 30 x Rs. 5 + 30 x 50 paise

= Rs. 150 + Rs. 15 = Rs. 165

 (E) Astha wants some Hong Kong Dollars and Won.

  a.  How many Won can she change for Rs. 4? For Rs.400?

Ans. Since 1 won = Re. 0.04

Multiply both sides by 100, we get

100 x 1 Won = 100 x Re. 0.04

= 100 x 4 paise

= 400 paise = Rs. 4

 For Rs.4, Astha can acquire 100 Won

And, for Rs.400, she can have 100x 100 = 10000 won

 b.  How many Hong Kong Dollars can she change for Rs. 508?

Ans. Since 1 Dollar (HK) = Rs. 5.10

It can be written as

= 5 rupees 10 paise

= 5 × 100 + 10 paise

= 500 + 10

= 510 paise

So, the total money with Astha = Rs 508

We can write it as

= 508 × 100

= 50800 paise

Here,  50800 paise = 50490 + 310 paise

By further calculation,

= 510 × 99 + 310 paise

= 510 HKD + 310 paise

We get,  310 paise = 300 paise + 10 paise = 3 rupees 10 paise = Rs 3.10

Therefore, Astha can change 99 HK Dollars for Rs 508, and Rs 3.10 is left with her.

 2.  Kiran went shopping with Rs. 200. Look at the bill. The shopkeeper forgot to put the point correctly in the prices. Put the point in the correct place and find out the total amount of the bill.

Ans. The correct bill as under:

3. Which city is cool?

 The temperature in each city was noted at 3pm on 16 January, 2008.

(a) Which place had the highest temperature at 3 pm? Which place is the coolest at that time?

Ans: Mumbai had the highest temperature at 3 pm. Srinagar had the coolest temperature at 3 pm.

 (b)  How much higher is the temperature in Mumbai from that in Srinagar?

Ans: The temperature in Mumbai is higher  than that in Srinagar by (35.1^o C - 8.1^o C) = 27^o C.

 (c) How many degrees will the temperature need to rise for it to reach 40^o C in Thiruvananthapuram?

Ans:  The temperature in Thiruvananthapuram needs to rise by 40°C - 33.5°C = 6.5°C to reach 40°C.

 (d) How much lower is the temperature of Kolkata from that in Chennai?

Ans:  The temperature in Kolkata is lower than in Chennai by 29.9^oC - 26.6^o C = 3.3^o C.

 (e) The temperature in these cities was also noted at 3 am on the same day, Look at the table and answer the questions.

 (i) Which place had the lowest temperature at 3 am? Imagine yourself to be there and describe how it would feel?

Ans. Srinagar had the lowest temperature at 3 am. It was very  cold and the water n pipes froze into ice. We  wore heavy woolen clothes and used fire for warmth.

 (ii) What is the difference between the temperatures at 3 pm and 3 am in Chennai? In Bhopal?

Ans. The difference between the temperatures at 3 pm and 3 am in Chennai is 29.9^o C - 21.1^oC = 8.8^oC.