# 3rd Grade - Solving Problems Using Relationships

 Grade Level: 3rd Skill: Problem Solving Topic: Solving Problems Using Relationships Goal: Find the total cost of multiple items, given the cost per unit. Skill Description: Algebra and Functions: solving problems between two quantities The ability to calculate how much a group of identical items costs if the price of one of them is known.

## Building Blocks/Prerequisites

### Sample Problems

 (1) If one toy car costs \$2.00, how much do 3 cars cost? (\$6.00) (2) If a pound of candy costs \$8.25, how much will you pay for 2 pounds? (\$16.50) (3) If the price of oranges is 2 oranges for \$.75, how much will 6 oranges cost? (\$2.25) (4) If a Playstation game costs \$25.83 how much will 2 games cost? (\$51.66) (5) If dog food costs \$3.63 a box and your dog can eat 3 boxes in a week how much will it cost to feed your dog each week? (\$10.89)

### Online Resources

 (1) (2) (3) (4)

### Extra Help Problems

(1)
 Complete this chart: Cost per item Number of Items Total Cost 1 \$1.25 3 (\$3.75) 2 \$ .99 7 (\$6.93) 3 \$ 2.15 2 (\$4.30) 4 \$ 6.29 1 (\$6.29) 5 \$ 9.00 80 (\$720.00) 6 \$1.10 4 (\$4.40) 7 \$3,99 8 (\$31.92) 8 \$ 9 12 (\$108) 9 \$6.35 6 (\$38.10) 10 \$ 2.30 7 (\$16.10) 11 \$10.00 2 (\$20.00) 12 \$ ,60 9 (\$5.40) 13 10 cents 19 (\$1.90) 14 \$15.01 2 (\$30.02) 15 \$ .80 2 (\$1.60) 16 \$ 2.99 8 (\$23.92) 17 \$ 4 2 (\$8) 18 \$8.22 8 (\$65.76) 19 \$ 9.24 3 (\$27.72) 20 Fifteen cents 9 (\$4.50) 21 Fifty cents 60 (\$30) 22 \$6.78 3 (\$20.34) 23 \$1.00 7 (\$7) 24 \$1.96 2 (\$3.92) 25 \$8.55 1 (\$8.55)