Depth · one concept from first principles · step 2 of 4

Combine two graphs to find totals

Mr. Park's class surveyed the number of each snack they bought at the school store and the price of one of each snack. The results are shown in the two bar graphs below. Find how much money the class spent buying bread.

Number of snacks bought (unit: items)

Snack	Crackers	Juice	Bread	Ice cream
Count	$12$	$14$	$16$	$10$

Price of one snack (unit: dollars)

Snack	Crackers	Juice	Bread	Ice cream
Price	$\$1.00$	$\$0.80$	$\$0.70$	$\$1.20$

The data are shown as two bar graphs. The first (horizontal) bar graph shows how many of each snack were bought; the second (vertical) bar graph shows the price of one of each snack in dollars.

Measurement & dataOperations

Your answer

dollars

How to solve

Strategy Analyze the Units — The two graphs supply different units - items and dollars-per-item - and linking the right bread values multiplies to dollars. Checking units (items times dollars/item = dollars) confirms the setup, and reading the matching bread bars is the key subproblem.

1STEP 1

Read bread's count

From the 'number of snacks bought' graph, bread was bought 16 times.

bread count = 16

2STEP 2

Read bread's unit price

From the 'price of one snack' graph, one bread costs $0.70.

bread price = $0.70

3STEP 3

Check the units and multiply

Total money = number of breads times price of one bread. Units: 16 items times $0.70 per item gives dollars. Compute 16 times 0.70.

16 × $0.70 = $11.20

Answer

11.20 dollars

16 × $0.70 = $11.20

16 breads at about $0.70 each should land close to 16 times 0.70 = 11.20; estimating with 16 times 0.75 = 12 confirms 11.20 is in the right range, in dollars.

Takeaway

Pull bread's number from one graph and bread's price from the other, then multiply count times price - linking two graphs is just Grade 4 cost = number times price!

Read bread's count
Read bread's unit price
Check the units and multiply

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