Mach each word problem from the top and bottom of the equation.

Question

A. A maple tree with a diameter of 12 inches has 32 rings inside it's trunk. How many rings would be expected in the Maple tree with a diameter of 20 inches?

B. If 10 bagels cost $3.69, how much will 12 bagels cost?

C. Approximately 3 people out of every 25 are left-handed. About how many left-handed people would you expect in a group of 140 people?

D. If it takes an old computer 15 minutes to download a 45 minute Tv show, how long would it take to download a 2 hour movie?

(Match each other top and bottom)

3.69/10=x/12

10/3.69 = x/12

32/12 = 20/x

15/45 =x120

15/45= x/2

3/25= x/140

32/12= x/20

3/25 = 140/x

Answer 1

A) 12in/32 rings = 20 in/x rings

The key to these problems is to make sure you are comparing the same things. One way to ensure this is to label your problem like I did above (i.e. inches & rings in this problem). Make sure the same label is in the numerator on both sides of the equation & in the denominator on both sides. In this example inches are in the numerator on both sides & rings are in the denominator. So we are comparing inches/rings on both sides of the equation. It does not matter what is in the numerator or denominator, they just have to be the same. You could literally do 32 rings/12 in = x rings/20 in.

B) You could set this problem up like a ratio ($3.69/10 bagels = $x/12 bagels) or you could divide $3.69 by 10 to find the cost of 1 bagel & then multiply that by 12 to find the cost of 12 bagels.

C) 3 left handed/25 people = x left handed/140 people

D) 15 min download/45 min show = x min download/120 min show

This problem has a trick. You have to make sure that the units are the same. You cannot compare minutes & hours. You need to multiply the 2 hours by 60 minutes to get both sides of the equation into minutes, then set up your ratio. ***The answers do not have this ratio. The division sign was left out of the right side of the equation***

Answer 2

The important thing to remember in these problems is keeping the similar information in the same place in each fraction. If the number of items is the numerator in one fraction, the number of items must be the numerator in the second. Example - items / money = items / money. Items / money will NEVER = money / items.

A. 32 rings / 12 inches = x rings / 20 inches - if the number of rings is the numerator in the first fraction, the number of rings MUST be the number of rings in the second fraction.

B $3.69 / 10 bagels = X money / 12 bagels - money over bagels = money over bagels

C. 3 lefthanders / 25 people = x lefthanders / 140 people

D. This one is a little different because of your units. There is 15 minute download time for 45 minute program. Then there is a 2 hour program. First, we must change this 2 hours into minutes. 2 hours = 120minutes. Now, we have 15 minute download time / 45 minute program and x minutes download time for a 120 minute program. And your equation looks like 15 minutes / 45 minutes = x minutes / 120 minutes.

NOTE - you see that equation 15/45 = x/2? When your units are different, you can bet there will be this incorrect equation as part of your choices. Be careful and pay attention to your units.