Unit Test: Number Play

Time: 1 hour M.M. 20 

Attempt all questions. 

• Question numbers 1 to 5 carry 1 mark each. 
• Question numbers 6 to 8 carry 2 marks each. 
• Question numbers  9 to 11 carry 3 marks each. 

Q1: What is the estimated sum of 645 + 876?    (1 mark)
(a) 1300
(b) 1400
(c) 1500
(d) 1600

Q2: What is the estimated difference of 812 - 493?    (1 mark)
(a) 200
(b) 250
(c) 300
(d) 350

Q3: Which of the following sets of numbers adds up to 24,539?    (1 mark)
(a) 5-digit number = 21,000, 3-digit number = 539
(b) 5-digit number = 20,000, 3-digit number = 439
(c) 5-digit number = 24,000, 3-digit number = 539
(d) 5-digit number = 19,000, 3-digit number = 539

Q4: Which of the following is a 3-digit palindrome that can be formed using the digits 1, 2, and 3?    (1 mark)
(a) 111
(b) 122
(c) 123
(d) 132

Q5: Which of the following numbers has digits that add up to 14?    (1 mark)
(a) 59
(b) 67
(c) 85
(d) 92

Q6: Calculate the digit sums of 3-digit numbers whose digits are consecutive (for example, 234, 345). Do you see a pattern? Will this pattern continue?    (2 marks)

Q7: The time now is 02:15. How many minutes until the clock shows the next palindromic time? What about the one after that?   (2 marks)

Q8. We are the group of 5-digit numbers between 40,000 and 80,000 such that all of our digits are even. Who is the largest number in our  group? Who is the smallest number in our group?  (2 marks)

Q9: What is the sum of the smallest and largest 5-digit palindrome? What is their difference?    (3 marks)

Q10. Digit sum 18.     (3 marks)
(a) Write other numbers whose digits add up to 18.
(b) What is the smallest number whose digit sum is 18?
(c) What is the largest 5-digit number whose digit sum is 18?
(d) How big a number can you form having the digit sum 18? Can you make an even bigger number?

Q11. Will reversing and adding numbers repeatedly, starting with a 2-digit number, always give a palindrome?      (3 marks)

​The Solutions of the Unit Test Here