Question. There were 90 people at the summer picnic. There were 50 soda cans, 50 plastic bottles of sparkling water, and 50 glass bottles of juice. One-half of the guests drank soda, one-third of the guests drank sparkling water, and four-fifths of the juices were consumed. How many recyclable cans and bottles were collected?
Answer. 115
What step-by-step reasoning justifies that answer?
Reasoning: The soda cans were consumed by 90 / 2 = 45 guests. The sparkling water was consumed by 90 / 3 = 30 guests. The juice bottles were consumed by 4 / 5 x 50 = 40 guests. In total there are 45 + 30 + 40 = 115 recyclable cans and bottles.