Alice and the Ping Pong Balls

By Page Bird

EMAT 6690


Alice bought a number of Ping-Pong
balls in a store where a 5 percent sales tax is added to every purchase. If she did not have to pay tax, she could have bought three more balls for the same amount of money. How many balls did she buy?
After thinking of this problem and trying to solve it using GSP, I came to the conclusion that an algebraic approach would be the simplest way to approach this problem.

Therefore, I took an algebraic approach:
p is the price of a ball and b is the number balls purchased

p* (b + 3) = 1.05*p * b
( b + 3 ) = 1.05*b
3 = 1.05*b - b
3 = .05 *b
3/ .05 = b
60 = b
So based on this, Alice bought 60 balls and she could have bought 63 balls at the same price had she not had to pay a 5% sales tax.



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