IXL | Guess-and-check problems

A plumber bought some pieces of copper and plastic pipe. Each piece of copper pipe was 8 meters long and each piece of plastic pipe was 3 meters long. He bought 4 pieces of pipe. The total length of the pipe was 17 meters. How many pieces of each type of pipe did the plumber buy?

pieces of copper pipe

pieces of plastic pipe

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Learn with an example

question

Eddie sliced 7 cakes. Each chocolate cake had 5 slices and each lemon cake had 7 slices. If Eddie made 41 slices in total, how many of each type of cake did he slice?

chocolate cakes

lemon cakes

solution

Use guess-and-check to solve the problem. Guess pairs of numbers that add up to 7.

Guess #1: 2 chocolate cakes and 5 lemon cakes

Find the number of cakes:

2 + 5 = 7

Find the total number of slices:

(5 × 2) + (7 × 5) = 10 + 35 = 45

The guess is incorrect. Try another guess.

Guess #2: 6 chocolate cakes and 1 lemon cake

Find the number of cakes:

6 + 1 = 7

Find the total number of slices:

(5 × 6) + (7 × 1) = 30 + 7 = 37

The guess is incorrect. Try another guess.

Guess #3: 4 chocolate cakes and 3 lemon cakes

Find the number of cakes:

4 + 3 = 7

Find the total number of slices:

(5 × 4) + (7 × 3) = 20 + 21 = 41

The guess is correct. Eddie sliced 4 chocolate cakes and 3 lemon cakes.

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Teacher tools

Work it out

Not feeling ready yet? These can help:

I.4Multi-step word problems

Evaluate numerical expressions with and without parentheses

M.11Find two numbers based on sum, difference, product, and quotient

N.11Solve word problems using guess-and-check

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