The task is to generate the correct answer for a given math problem.

Q: Problem: a car salesman earns a base salary of $ 1000 per month plus a commission of $ 200 for each car he sells . if the car salesman earned $ 2000 in march , how many cars does he need to sell in april in order to double his march earnings ?

A: 15
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Q: Problem: an aeroplane covers a certain distance of 670 kmph in 6 hours . to cover the same distance in 6 1 / 4 hours , it must travel at a speed of

A: 643
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Q: Problem: how many digits are in ( 8 × 10 ^ 18 ) ( 10 × 10 ^ 10 ) ?

A:
3
****