Question

A student collects post cards from around the world. She has 150 post cards. Of these post cards, 42% are from Africa, 20% are from Europe, 10% are

from Asia, and the rest are from South America. How many post cards are from South America?

Answer 1

42 post cards

Explanation:

First, let's find how many cards are from each country by multiplying the decimal forms of the percent by the total number of post cards (150).

Reminder: to get the decimal form of a percent you move the decimal point twice to the left!

Africa: (.42)(150) = 63

Europe: (.20)(150) = 30

Asia: (.10)(150) = 15

Add all of them

63 + 30 + 15

= 108

Subtract it from the total

150 - 108

= 42

Another way to do this is to add up the percent's and then subtract it from 100, convert that to decimal form and multiply it by 150. Like this:

42% + 20% + 10% = 72%

100 - 72 = 28

(.28)(150) = 42

Therefore, 42 post cards are from South America.

I hope this helps!!

- Kay :)

Answer 2

The answer is 42.

Start by adding the percentages you have:
42 + 20 + 10 = 72% Subtract that from 100, and you have 28% left. That percentage is from South America.

To get the number of cards from SA, multiply the 150 postcards by 0.28 (the decimal for 28%) to get 42.