Peter purchased 14 new baseball cards for his collection. This increased the size of his collection by 35%. How many baseball cards does Peter now have?

Peter now has 54 baseball cards

Step-by-step explanation:

Percentages

Assume Peter had x baseball cards in his collection. The 35% of his initial collection is

35 * x / 100 = 0.35x

We know that those 14 new baseball cards represent a 35% of his previous collection, therefore we can set a simple equation

0.35x=14

When we solve for x, we'll know how many baseball cards Peter had before

x=14 / 0.35 = 40

Peter had 40 cards, he added 14 new baseball cards, so he now has 40+14=54

Peter now has 54 baseball cards