Answer:
10 inches.
Step-by-step explanation:
One stack has boxes that are 2 inches high, then the height of this stack can be only multiples of 2 inches.
The other stack has boxes that are 5 inches high, then the height of this stack can be only multiples of 5 inches.
The height of both stacks will be the same for all the common multiples of 2 and 5.
Because 2 and 5 are prime numbers, all the common multiples between 2 and 5 will be direct products of these two numbers.
Like 2*5 = 10
is both a multiple of 2 and 5 (is the first common multiple)
Then we can use stacks of 10 inches.
Such that, for the stack where each box is 2 inches high, we need:
10in/2in = 5
5 boxes.
And for the stack where each box is 5 inches high, we will need:
10in/5in = 2
2 boxes.
