Hi, could anybody help me with below question? Why is is not (10+60)(10+80) = 70 x 90 = 6,300 for the walkway area? Thanks in advance! 
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A new exhibit at a zoo is rectangular and measures 60 feet by 80 feet. An observation walkway around the whole exhibit will be added that is 10 feet wide. If it takes 1 ton of concrete to pave 10 square feet of walkway, how many tons of concrete will be needed to pave the entire walkway?
â—‹ 150
â—‹ 240
â—‹ 320
â—‹ 480
â—‹ 2,400
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Solution:
We can find the area of the walkway by subtracting the smaller rectangle, the dimensions of which we are given in the question as 60 by 80, from the area of the big rectangle, the area that will include the proposed walkway.
We can find the area of the walkway by subtracting the smaller rectangle, the dimensions of which we are given in the question as 60 by 80, from the area of the big rectangle, the area that will include the proposed walkway.
Since the 10-foot-wide walkway will completely surround the exhibit, we will have to add 2 x 10 = 20 to both the length and the width given in the question.
The area of the large rectangle is therefore (20+60)(20+80) = 80 x 100 = 8,000.
The area of the small rectangle is 60 x 80 = 4,800.
The area of the walkway = 8,000 - 4,800 = 3,200 square feet.
One ton of concrete is required for every 10 square feet, so 3200 / 10 = 320 tons of concrete.
Answer choice (C) is correct.
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A new exhibit at a zoo is rectangular and measures 60 feet by 80 feet. An observation walkway around the whole exhibit will be added that is 10 feet wide. If it takes 1 ton of concrete to pave 10 square feet of walkway, how many tons of concrete will be needed to pave the entire walkway?
â—‹ 150
â—‹ 240
â—‹ 320
â—‹ 480
â—‹ 2,400
-
Solution:
We can find the area of the walkway by subtracting the smaller rectangle, the dimensions of which we are given in the question as 60 by 80, from the area of the big rectangle, the area that will include the proposed walkway.
We can find the area of the walkway by subtracting the smaller rectangle, the dimensions of which we are given in the question as 60 by 80, from the area of the big rectangle, the area that will include the proposed walkway.
Since the 10-foot-wide walkway will completely surround the exhibit, we will have to add 2 x 10 = 20 to both the length and the width given in the question.
The area of the large rectangle is therefore (20+60)(20+80) = 80 x 100 = 8,000.
The area of the small rectangle is 60 x 80 = 4,800.
The area of the walkway = 8,000 - 4,800 = 3,200 square feet.
One ton of concrete is required for every 10 square feet, so 3200 / 10 = 320 tons of concrete.
Answer choice (C) is correct.
