A student was asked to find 2/5th of a number and he instead multiplied it by 5/2. As a result he got an answer which was more than the correct answer by 5208. What was the number?

2485
2456
2480
2455

Correct Answer: 2480

Explanation:

Let the number be x. Then,
5x/2 - 2x/5 = 5208
⇒ (25x - 4x)/10 = 5208
⇒ 21x/10 = 5208
⇒ 21x = 5208 x 10
⇒ x = (5208 x 10)/21
⇒ x = 2480
So, the original numbers was 2480.

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