Please Helppp
Practice A
Directions: Use a calculator to find the cross products. Compare the cross products and determine if the ratios form a proportion. Write “Y” if the ratios do form a proportion, and write “N” if the ratios do not form a proportion.
1. 3/12 and 10/30
2. 7/16 and 42/66
3. 13/70 and 39/200
4. 16/34 and 80/170
5. 11/12 and 66/72
6. 14/17 and 112/134
7. 2/3 and 120/190
8. 23/99 and 115/495
Rule
You can use cross products to find an UNKNOWN TERM in a proportion. The letter ‘n’ stands for the missing value.
Example: Find the unknown value of ‘n’ using cross multiplication
\LARGE \frac{8}{n} \LARGE \frac{4}{6}
Cross multiply:
n x 4 = 4n
8 x 6 = 48
4n = 48
Solve for ‘n’ using basic algebra rules - divide each side by the coefficient 4
\LARGE \frac{4n}{4} = \LARGE \frac{48}{4}
n = 12
Substitute the value ‘12’ in the ratio for the unknown (n)
\LARGE \frac{8}{12} = \LARGE \frac{4}{6}
Check your work:
12 x 4 = 48
8 x 6 = 48
Practice B
Directions: Solve for the missing proportion in each of the following problems.
9. 12/n = 20/25
10. 5/8 = n/24
11. 2/3 = 16/n
12. 12/14 = n/21
13. n/10 = 6/15
14. 12/3 = 10/n
15. 5/n = 10/16
16. 12/8 = 4/n
Application: Proportions can be used to solve problems involving mixtures or comparisons. Make sure that you are careful to write the ratios in the same order.
Example:
Golden Yellow paint is made by mixing 2 parts yellow to 1 part red paint. How many pints of red paint should be mixed with 3 pints of yellow paint?
Step 1: Set up your ratio
\LARGE \frac{yellow}{red} \LARGE \frac{2}{1} = \LARGE \frac{3}{n}
Step 2: Cross multiply
1 x 3 = 3, and 2 x n = 2n, which equals 3 = 2n
Step 3: Remove the coefficient, divide by the coefficient (2)
\LARGE \frac{3}{2} = \LARGE \frac{2n}{2} = 1\LARGE \frac{1}{2} n
Step 4: You should use 1 ½ pints of red paint for every 3 pints of yellow paint.
Review the steps:
Step 1: Set up your ratio
Step 2: Cross multiply
Step 3: If there is a coefficient, then remove the coefficient by using basic algebra rules
Step 4: Write your answer statement.
Practice C
Directions: Use this method to solve application problems. Note: Be sure to set up your proportions correctly!
17. Lime Green pain is made by mixing 7 parts yellow to 3 parts blue. How much yellow should be mixed with 9 pints of blue?
18. Mix 3 quarts of water with 2 lemons to make lemonade. How many quarts of water are mixed with 1 lemon?
19. Mix 6 parts of cornstarch to 1 part water to make goo. How much water should be used with 2 cups of cornstarch?
20. Oranges sell for 12 oranges for a dollar. How much will 27 oranges cost?
21. On a map, 1 inch equals 15 miles. How many miles apart are two towns that are 6.4 inches apart on the map?
22. Sheila’s car gets 42 miles per one gallon of gas. How much gas will she use on a 575-mile trip?
23. Mark can drive 250 miles in 4 hours. How far can he drive in 6 hours?
24. At a music concert, there were 5 females for every 4 males. If there were 300 females, how many males attended the concert?
25. If one US dollar equals $.85 in foreign currency, then what would $10.71 in foreign currency equal in US currency?
--
1. If there are 6 diesel cars sold to every 3 regular gasoline cars, is it the same proportion as 2 diesel cars to every 1 regular gasoline car? Explain your answer.
A) No
B) Yes
2. Each hour a vet usually sees 4 cats, 1 dog, and 5 rabbits. Choose the correct way of writing this as a ratio.
A) 4:1:5
B) 1:5:4
C) 5:4:1
3. 7 out of 10 women prefer Brand A moisturizer and the other 3 prefer Brand B. Choose how this should be written as a ratio of Brand A to Brand B.
A) 7: 3
B) 7:10
C) 3:10
4. The instructions on a bottle of orange squash say to a mix of one part of the squash with three parts of water. Choose the correct way of writing this as a ratio.
A) 3:1
B) 1:3
C) 1:4
5. An extra used in a TV show is paid $100 for 2 days 'on set'. How much would the extra earn for 4 days 'on set'?
A) $250
B) $400
C) $200
6. In an exercise class, there are 9 women and 3 men. What is the ratio of women to men?
A) 4:1
B) 1:3
C) 3:1
7. A dog training lead adjusts 2 ways, to 160cm or 80cm. Choose the simplest way of writing this as a ratio.
A) 2:1
B) 16:8
C) 160:80
8. Sarah and Winston buy the same brand of T-shirts from different stores. Sarah pays $8 and Winston pays $4. Choose the simplest way of writing this as a ratio.
A) 2:4
B) 2:1
C) 8:4
9. There are 9 sheep in a farming show. There are only 3 sheep pens. If the sheep are divided equally between the pens what is the ratio of sheep to each sheep pen?
A) 3:3
B) 1:3
C) 3:1
10. An older dolphin catches three times as many fish as a young dolphin during a feeding frenzy. If the young dolphin catches 8 fish, how many fish does the older dolphin catch?
A)24
B)64
C) 16
