Find the surface area of the cube (above) using its net (below).
1 answer:
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Answers:
- The lengths of sides PQ and RS are <u> 13 </u>
- The lengths of sides QR and SP are <u> </u><u>20 </u>
This is a 13 by 20 rectangle.
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Explanation:
Refer to the drawing below.
Let x be the length of side SP. Since we're dealing with a rectangle, the opposite side is the same length. Side QR is also x units long.
We're told that RS = SP - 7 which is the same as saying RS = x-7
We also know that PQ = x-7 as well because PQ is opposite side RS.
In short, we have these four sides in terms of x
- PQ = x-7
- QR = x
- RS = x-7
- SP = x
as shown in the drawing. The four sides add up to the perimeter of 66.
PQ+QR+RS+SP = perimeter
PQ+QR+RS+SP = 66
(x-7)+x+(x-7)+x = 66
4x-14 = 66
4x = 66+14
4x = 80
x = 80/4
x = 20
Use this x value to find the unknown side lengths.
- PQ = x-7 = 20-7 = 13
- QR = x = 20
- RS = x-7 = 20-7 = 13
- SP = x = 20
In short, this is a 13 by 20 rectangle.
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Check:
perimeter = side1+side2+side3+side4
perimeter = PQ+QR+RS+SP
perimeter = 13+20+13+20
perimeter = 33+33
perimeter = 66
The answer is confirmed.
