Ratios Introduction — Answer Key
Part A: Multiple Choice
Circle the best answer for each question.
1. A class has 12 boys and 16 girls. What is the part-to-part ratio of boys to girls in simplest form?
A) 3:4
B) 4:3
C) 12:28
D) 3:7
12:16 simplifies to 3:4 by dividing both parts by 4, which is the part-to-part ratio.
2. A bag has 5 red and 3 blue marbles. What is the part-to-whole ratio of red marbles to all marbles?
A) 3:8
B) 5:8
C) 5:3
D) 8:5
Total marbles is 8, and 5 are red, so the part-to-whole ratio is 5:8.
3. A recipe uses flour and sugar in a 3:2 ratio. If you use 9 cups of flour, how much sugar do you need?
A) 4 cups
B) 5 cups
C) 6 cups
D) 8 cups
Scaling 3:2 by 3 gives 9:6, so 9 cups flour needs 6 cups sugar.
4. In a class of 28 students, the ratio of boys to girls is 3:4. How many boys are in the class?
A) 7
B) 10
C) 16
D) 12
28 divided by 7 parts is 4 per part; 3 parts of boys gives 12 boys total.
Part B: Fill in the Blank
Write the correct answer on each line.
1. If 2:5 is the ratio of cats to dogs and there are 10 cats, then there are 25 dogs.
Scaling 2:5 by 5 gives 10:25, so there are 25 dogs.
2. A team has 9 wins and 6 losses; the simplest part-to-part ratio of wins to losses is 3:2.
9 and 6 share factor 3; dividing gives 3:2, the simplest form.
3. A jar has 4 red, 3 blue, and 5 green beads; the part-to-whole ratio of blue to all is 3:12.
There are 12 beads total and 3 are blue, giving the part-to-whole ratio 3:12.
4. Paint mix is 2:3 blue to white. For 12 cups of white, you need 8 cups of blue.
Scaling 2:3 by 4 gives 8:12, so 12 cups of white needs 8 cups of blue.
5. In a class of 30, the ratio of boys to girls is 2:3; the number of girls is 18.
30 divided by 5 parts is 6 per part; 3 parts of girls gives 18 girls.