# How can 2 3 be calculated

### Calculate fractions

Leonie needs a new bike. At the dealer she saw a used cross bike that costs \$ 160 \$. Her father says that if Leonie can collect \$ 3/4 \$ of the money himself, he'll add the rest. Now Leonie is wondering how much money she has to save herself.

So you determine the fraction \$\$ 3/4 \$\$ of the \$\$ 160 \$\$ €. The \$\$ 160 \$\$ € are the whole.

Divide the whole thing into 4 parts. You determine \$\$ 1/4 \$\$.

Mathematically: Divide \$\$ 160 \$\$ € by the denominator.
\$\$160\$\$ € \$\$:\$\$ \$\$4 = 40\$\$ €.

Take 3 parts. You determine \$\$ 3/4 \$\$.

Mathematically: \$\$ 40 \$\$ € \$\$ * \$\$ \$\$ 3 = 120 \$\$ €

So Leonie has to save \$ 120 \$. Then she gets the rest of it.

Image: fotolia.com (Franz Pfluegl)

### The calculation method

So the fraction (\$\$ 3/4 \$\$) tells you how to do the math:

1. Divide the whole thing.
\$\$160\$\$ € \$\$:\$\$ \$\$= 40 \$\$ €

2. You take the result with you.
\$\$40\$\$ € \$\$* \$\$ \$\$= 120\$\$ €

How to calculate the fraction:

1. Divide the whole thing.
2. Multiply the result by.

### That's how it works!

In some cases it is easier to reverse the two steps, so

1. Take the whole thing with you.
2. Share the result by.

Example:
Philipp likes to eat fish fingers. However, he has found that his father burns about \$\$ 2/6 \$\$ fish fingers in a pack of \$\$ 15 \$\$ pieces.

\$\$ 15 \$\$ (the whole) cannot be easily divided by. But if you take \$\$ 15 \$\$ with you first, you will get \$\$ 30 \$\$.

\$\$15\$\$ \$\$*\$\$ = \$\$30\$\$

Now sharing is easier.

\$\$30 :\$\$ \$\$= 5\$\$

So many fish fingers burned! Poor Philip!

kapiert.decan do more:

• interactive exercises
and tests
• individual classwork trainer
• Learning manager

### Shorten, shorten

Take a close look at the fraction first: if you can shorten it, always do it. Then you can calculate with smaller numbers.

In the case of Philip's fish finger fiasco, it would have looked like this:

\$\$2/6 = (2:2)/(6:2) = 1/3\$\$

Here the counter is even \$\$ 1 \$\$. Then you just have to divide the whole thing through, because you don't have to take it with me anymore.

\$\$15\$\$ \$\$ :\$\$ \$\$= 5\$\$

So you get the same result.

Don't forget: smaller numbers make arithmetic easier! :)