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Suppose the average weight of9 persons is 50 kg. The average weight of the first5 persons is 45 kg, whereas the average weight of the last 5 persons is 55 kg. Then the weight of the5th person will be
  • a)
    45 kg
  • b)
    47.5 kg
  • c)
    50 kg
  • d)
    52.5 Kg
Correct answer is option 'C'. Can you explain this answer?
Verified Answer
Suppose the average weight of9 persons is 50 kg. The average weight of...
Weight of fifth person = (5 × 45 + 5 × 55) – 9 × 50   
= (225 + 275) – 450   
= 500 – 450 = 50 kg
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Most Upvoted Answer
Suppose the average weight of9 persons is 50 kg. The average weight of...
Given Information:
- The average weight of 9 persons is 50 kg.
- The average weight of the first 5 persons is 45 kg.
- The average weight of the last 5 persons is 55 kg.

To find: The weight of the 5th person.

Solution:
Let's assume the weight of the 9 persons are as follows -

- w1, w2, w3, w4, w5, w6, w7, w8, w9

Now, we can use the formula for the average weight of n persons, which is:

Average weight of n persons = (Sum of weights of all persons) / n

Using this formula, we can write the following equations -

- (w1 + w2 + w3 + w4 + w5 + w6 + w7 + w8 + w9) / 9 = 50 (Average weight of 9 persons is 50 kg)
- (w1 + w2 + w3 + w4 + w5) / 5 = 45 (Average weight of the first 5 persons is 45 kg)
- (w5 + w6 + w7 + w8 + w9) / 5 = 55 (Average weight of the last 5 persons is 55 kg)

We can simplify these equations as follows -

- w1 + w2 + w3 + w4 + w5 + w6 + w7 + w8 + w9 = 450 (Multiplying both sides by 9)
- w1 + w2 + w3 + w4 + w5 = 225 (Multiplying both sides by 5)
- w5 + w6 + w7 + w8 + w9 = 275 (Multiplying both sides by 5)

Subtracting equation 2 from equation 1, we get -

- w6 + w7 + w8 + w9 = 225 (Subtracting both sides by w1 + w2 + w3 + w4 + w5)

Subtracting equation 3 from equation 1, we get -

- w1 + w2 + w3 + w4 = 175 (Subtracting both sides by w5 + w6 + w7 + w8 + w9)

Now, we need to find the weight of the 5th person, which is w5.

Adding equations 2 and 3, we get -

- w5 + w6 + w7 + w8 + w9 + w1 + w2 + w3 + w4 = 500 (Adding both sides)

Substituting the values we have found earlier, we get -

- w5 + 275 + 225 = 500 (Substituting w5 + w6 + w7 + w8 + w9 = 275 and w1 + w2 + w3 + w4 = 175)

Simplifying, we get -

- w5 = 50

Therefore, the weight of the 5th person is 50 kg, which is option C.
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Suppose the average weight of9 persons is 50 kg. The average weight of the first5 persons is 45 kg, whereas the average weight of the last 5 persons is 55 kg. Then the weight of the5th person will bea)45 kgb)47.5 kgc)50 kgd)52.5 KgCorrect answer is option 'C'. Can you explain this answer?
Question Description
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