Hint
You might find Pythagoras' theorem very useful [a2 + b2 = c2].
Answer
148 inches.
We can use Pythagoras' theorem if we draw an imaginary line across to create a right-angled triangle.
The hypotenuse is equal to the rope's length R. The bottom of the triangle is 48 inches. The vertical side is R − 8 (the difference between 20 inches and 12 inches).
Pythagoras' theorem tells us that:
a2 + b2 = c2
Where c is the hypotenuse.
This gives us:
482 + (R − 8)2 = R2
2304 + (R − 8)(R − 8) = R2
2304 + R2 − 16R + 64 = R2
2304 − 16R + 64 = 0
16R = 2368
R = 148
As required.
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Puzzle 2
Three builders are laying a brick wall.
Freddie can lay 1,000 bricks in three hours, Jimmy can lay 1,000 bricks in two hours and Kevin can lay 1,000 bricks in six hours.
How long will it take Freddie, Jimmy, and Kevin to lay 1,000 bricks if they all work together?
