Question

Your friend used the proportion 40/100 = 80/? To find 40% of 80 and says that the answer is 200. Complete the explanation as to why your friend is incorrect and find the correct answer.

Answer 1

Answer: See explanation

Explanation:

My friends calculation is wrong. 40% of 80 is not 200. It is:

= 40% of 80

= 40/100 × 80

= 0.4 × 80

= 32

He should have represented the missing number by x. Therefore,

40/100 = 80/x

Cross multiply

(40 × x) = (80 × 100)

40x = 8000

x = 8000/40

x = 200