Question

Dev thinks of a whole number. He multiplies it by 4. He rounds his answer to the nearest 10. The result is 50. Write all the possible number that Dev could have started with.

Answer 1

{12, 13}

Explanation:

Whole numbers that round to 50 will be in the range 45 to 54. Multiples of 4 in that range are 48 and 52.

48 = 4·12

52 = 4·13

Dev's number could be either 12 or 13.