Answer:
B - The surface area is multiplied by 4.
Explanation:
The first step is to figure out the original surface area of the shape using this formula;
A = 2(wl + hl + hw)
Which in this problem, means:
A = 2 (5 × 9) + 2 (3 × 9) + 2 (3 × 5) = 174.
Now, we must figure out the surface area once the measurements are doubled, using the same equation:
A = 2 (10 × 18) + 2 (6 × 18) + 2 (6 × 10) = 696.
If we then take a look back at the original surface area, we can already tell the answer is not D, as 696 is too high to be double 174, considering 150 × 2 is 300, and 24 × 2 is 28.
We can also eliminate option A, as it's clear multiplying 174 by 8 would take us into the thousands, since 8 × 100 is 800, and already over our target.
So we're left with two options - Multiplied by 4, or multiplied by 6.
If we know that multiplying 174 by 8 would take our answer into the thousands, it's also safe to assume multiplying by 6 would do the same, because 6 × 100 is 600, and multiplying 74 by 6 would take us way over target, too.
However, just to be on the safer side, we can divide 696 by 6;
696 ÷ 6 = 116.
Now we have eliminated answer C.
So the answer is B - The surface area is multiplied by 4.
(Confirmation -
696 ÷ 4 = 174
174 × 4 = 696)
Hope this helped!