Stephanie M. answered 04/21/15
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First, let's change those measures into numbers that are easier to work with. 8 inches is 8/12 = 2/3 feet, and 6 inches is 6/12 = 1/2 feet. So, the garden is 30 2/3 feet wide and 40 1/2 feet long.
To find the length of the diagonal, you'll need to treat this as a right triangle with legs 30 2/3 and 40 1/2 and hypotenuse x. Then you can use the Pythagorean Theorem (a2 + b2 = c2) to solve for the hypotenuse:
(30 2/3)2 + (40 1/2)2 = x2
940 4/9 + 1640 1/4 = x2
940 16/36 + 1640 9/36 = x2
2580 25/36 = x2
x = 50.8 feet (approximately)
So, if Shariff walks around the whole garden and down the diagonal, she walks the width twice, the length twice, and the diagonal once. In other words:
2(30 2/3) + 2(40 1/2) + (50.8) = 61 1/3 + 81 + 50.8 = 193.13 feet (approximately)