Question

Explain why it is possible to draw more than two different rectangles with an area of 100 square units, but it is not possible to draw more than two different rectangles with an area of 55 square units. The sides of the rectangles are whole numbers.

Answer 1

Answer:

100 has more divisors than 55.

Step-by-step explanation:

The prime factorization of 100 is ...

... 100 = 2²×5²

The number of divisors of 100 is the product of the exponents of these factors, after each has been increased by 1: (2+1)(2+1) = 9. Those divisors are ...

... 1, 2, 4, 5, 10, 20, 25, 50, 100

A rectangle can be formed with each divisor as the length of a side. If we count 1×100 and 100×1 as the same rectangle, then 5 different rectangles are possible:

... 1×100, 2×50, 4×25, 5×20, 10×10

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On the other hand, the prime factorization of 55 is ...

... 55 = 5¹×11¹

This means the number of divisors is (1+1)(1+1) = 4. Those divisors are ...

... 1, 5, 11, 55

The number of rectangles that can be formed from these is 2:

... 1×55, 5×11

100 has more divisors, so there are more ways that rectangles can be formed from them.