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Problem of the Week
Problem A and Solution
Playing Fetch


Leslie loves playing fetch with her dog Spencer. Spencer always starts by sitting beside Leslie before Leslie throws the ball. When Leslie throws the ball, Spencer runs to it and brings the ball back to the same spot. Leslie throws the ball three times.

How far does Spencer run in total?


On the first throw, Spencer runs \(2 \times 8 = 16\) metres.

The distance of the second throw is \(8 \times 2 = 16\) metres.
On the second throw, Spencer runs \(2 \times 16 = 32\) metres.

The distance of the third throw is \(16 - 5 = 11\) metres.
On the third throw, Spencer runs \(2 \times 11 = 22\) metres.

The total distance Spencer runs is: \(16 + 32 + 22 = 70\) metres.

We can also show the distance Spencer runs on a number line.

A number line measures 0 to 70. Six arrows are drawn above the line with the next arrow always starting where the previous arrow ended. The first arrow starts at 0 and the last arrow ends at 70. The arrows are labelled 8 metres, 8 metres, 16 metres, 16 metres, 11 metres, and 11 metres.