# Bruce collects stamps. He has six times as many 10-cent stamps as 5-cent stamps, and he has some 20-cent stamps as well. Bruce has 72 stamps which are worth $8.40. How many of each stamp does he have?

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Use tables to answer this question.

Use tables to answer this question.

##### 1 Answer

He has

Eight 5ȼ stamps

Forty-eight 10ȼ stamps

Sixteen 20ȼ stamps

#### Explanation:

Problems like this have two kinds of data

1) The NUMBER of stamps

2) The monetary VALUE of the stamps

.................

**First find a way to express the NUMBER of each kind of stamp**

Let

5ȼ stamps . . . . . . . . . . . . . .

6 times as many . . . . . . .

All the rest . . . . . . .

*Here is how to figure the number of 20ȼ stamps*

The number of 20ȼ stamps is the number remaining out of a total of 72 after you subtract the number of 5ȼ stamps as well as the number of 10ȼ stamps

Number of 20ȼ stamps . . . 72 stamps

Number of 20ȼ stamps . . .

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**Now find a way to express the VALUE of each kind of stamp**

.

6

........................

**The values of all these stamps add up to 840ȼ**

[ value of 5ȼ ] "plus" [ value of 10ȼ ] "plus" [ . .value of 20ȼ ] = 840

[ . . . .

*Solve for #x#, already defined as "the number of 5ȼ stamps"*

1) Collect like terms

2) Subtract

3) Divide both sides by

"the number of 5ȼ stamps"

The number of 10ȼ stamps is

**48 ← the number of 10ȼ stamps**

The number of 20ȼ stamps is "all the rest"

*and* minus (48 10ȼ stamps)

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Check

8 stamps @ 5ȼ ea . . . . 40ȼ

48 stamps @ 10ȼ ea . . . 480ȼ

16 stamps @ 20ȼ ea. . . .320ȼ

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72 stamps . . . . . . . . . . . .840ȼ

Check!