Basic Math

Question 1

Simple Ratios

The scale on a map is 7cm : 10km.

If the distance between two cities is 42 cm on the map, how far apart are the cities in km?

Answer 1

Find the multiple of the known (cm) and apply the same multiple to the unknown (km). 42 cm / 7 cm = 6

6 * 10 km = 60 km apart

Question 2

Simple Ratio word problems.

In a class, the girl to boy ratio is 5 to 8. If there are a total of 65 students how many girls are there?

Answer 2

If for every 5 girls there are 8 boys you need to realize that the fraction of girls to total students in each “unit” is 5/13. You need to determine the multiple of 13 that 65 is. 65/13 = 5. Then multiply 5 *5 = 25. Thus, there are 25 girls in the class of 65 studnents with this ratio.

Question 3

How to check if a number is divisible by another 3

Answer 3

Add up the terms and if the sum is divisible by 3 then the entire value is divisible by 3. (e.g. 189/3 - 1+8+9 = 18/3 = 6 therefore 189 is divisible by 3)