How many balls did the store originally order?

Question

A sporting goods store ordered an equal number of white and yellow tennis balls. The tennis ball company delivered 30 extra white balls, making the ratio of white balls to yellow balls 6:5. How many tennis balls did the store originally order?

Answer 1

b represents the original number of the white

b represents the original number of the yellow

(b + 30) : b :: 6 : 5     proportion

6b = 5(b + 30)            product means extremes

 

Can you solve for b?

 

 

 

 

Answer 2

the ratio 1:1 (one white for every one yellow) is the same as the ratio 5:5 (5 whites for every 5 yellows).

An increase of 30 balls on one side of the ratio made the result a ratio of 6:5 (an increase of 1 ratio point on the white side), so 1 of these ratio points equals 30 balls. Their initial order can be viewed in the ratio of 5:5 to keep the size of the ratio points the same so that means they ordered 5 sets of 30 white balls and 5 sets of 30 yellow balls or 150 white and 150 yellow (300 total).

 

Hope that helps :-)