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Calculate $9 for 1 1/2 pounds

Step by step, with the reason for every step · Unit rates with fractions · Foundations

Step by step

The question

Question: $9 for 1 and 1/2 pounds: how much is that per pound?

$9 for 112 pounds

A unit rate says how much for 1 pound.

Per pound means: divide by the pounds.

per pound = ÷ pounds

1 Write the rate

Dollars divided by pounds: 9 ÷ 1 and 1/2.

= 9 ÷ 112
dollars ÷ pounds

Careful!

Not the other way round.

That would be pounds per dollar.

Careful: not 112 ÷ 9 ✗

2 Divide

1 and 1/2 is a mixed number.

Each whole one is 2/2.

So we do 1 times 2, plus 1.

The bottom stays 2.

= 9 ÷ 1 × 2 + 12

1 times 2 plus 1 is 3.

So it is 3/2.

= 9 ÷ 32

Dividing by a fraction is the same as times its flip.

Keep the first number.

Change divide to times.

Turn the second fraction upside down.

÷ 32 → × 23

So 3/2 becomes 2/3, and divide becomes times.

= 9 × 23

Before we multiply, we make the numbers smaller.

9 on top and 3 at the bottom both divide by 3.

A top and a bottom divided by the same number: the answer stays the same.

9 and 3: ÷ 3 → 3 and 1

So we multiply smaller numbers.

= 31 × 21

3 times 2 is 6.

So the unit rate is $6 per pound.

= $6 per pound

3 Check

Let's check: $6 per pound, for 1 and 1/2 pounds.

6 times 3/2 is 9.

That is the price we started with.

So the answer is right!

$6 × 32 = $9

Let's look back.

First: write the rate.

Then: divide.

Last: check.

Answer
= $6 per pound

Your turn

Try this one yourself, then check:

$5 for 114 pounds
Show the answer
$4 per pound

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