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In a potato race, a bucket is placed at the starting point, which is 55m from the first potato, and the other potatoes are placed 33m apart in a straight line. There are 2020 potatoes in the line. Each competitor starts from the bucket, picks up the nearest potato, runs back with it, drops it in the bucket, runs back to pick up the next potato, runs to the bucket to drop it, and continues in the same way until all the potatoes are in the bucket. What is the total distance the competitor has to run?

Solution

✅ Correct Option: 1

The bucket is at the starting point, the first potato is 55m away, and the remaining 1919 potatoes are placed 33m apart in a straight line.


The distance from the bucket to each potato:

Distance to Potato 1=51 = 5m

Distance to Potato 2=5+3=82 = 5 + 3 = 8m

Distance to Potato 3=5+3+3=113 = 5 + 3 + 3 = 11m

Distance to Potato n=5+3(n−1)=2+3nn = 5 + 3(n-1) = 2 + 3nm


For each potato, the competitor must run to it and back to the bucket. The distance for each trip is twice the distance to that potato.

The total distance is:

Total=2×∑n=120(2+3n)\text{Total} = 2 \times \sum_{n=1}^{20} (2 + 3n)


Expanding the sum:

∑n=120(2+3n)=∑n=1202+∑n=1203n\sum_{n=1}^{20} (2 + 3n) = \sum_{n=1}^{20} 2 + \sum_{n=1}^{20} 3n

=2×20+3∑n=120n= 2 \times 20 + 3 \sum_{n=1}^{20} n

Using the formula ∑n=120n=20×212=210\sum_{n=1}^{20} n = \dfrac{20 \times 21}{2} = 210:

=40+3×210= 40 + 3 \times 210

=40+630= 40 + 630

=670= 670


The total distance:

Total distance=2×670=1340\text{Total distance} = 2 \times 670 = 1340 meters

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