2016 AMC8 答案

It is best to split 11 hours and 5 minutes into 2 parts, one of 11 hours and another of 5 minutes. We know that there is minutes in a hour. Therefore, there are minutes in 11 hours. Adding the second part(the 5 minutes) we get .

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Solution 1

Use the triangle area formula for triangles: where is the area, is the base, and is the height. This equation gives us .

Solution 2

A triangle with the same height and base as a rectangle is half of the rectangle's area. This means that a triangle with half of the base of the rectangle and also the same height means its area is one quarter of the rectangle's area. Therefore, we get .

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We can call the remaining score . We also know that the average, 70, is equal to . We can use basic algebra to solve for :giving us the answer of .

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When Cheenu was a boy, he could run miles in hours and minutes minutes minutes, thus running minutes per mile. When he is an old man, he can walk miles in hours minutes minutes, thus walking minutes per mile. Therefore it takes him minutes longer to walk a mile now compared to when he was a boy.

Solution 1

For the first three digits, there are combinations since is not allowed. For the final digit, any of the numbers are allowed.

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