Step by step
The question
Question: change $250 to euros, when $1 = €0.80.
$1 = €0.80. Change $250 to euros.
1 Write the rate
The rate says: 1 dollar is worth 0.80 euros.
$1 = €0.80
From dollars to euros, we multiply by 0.80.
Going back, we divide by 0.80.
dollars → euros: × 0.80
euros → dollars: ÷ 0.80
2 Multiply by the rate
Each dollar is worth €0.80.
250 dollars are worth 250 times as much.
$250 = 250 × €0.80
250 times 0.80 is €200.
= €200
To multiply decimals: first 250 times 80, as whole numbers.
That is 20000.
Then count the decimal places: 2.
250 × 80 = 20000
2 decimal places: 200
Careful!
Check the direction.
Dollars to euros: we multiply by the rate.
Careful: dollars → euros: × the rate
So $250 is €200.
3 Check
Let's check: change the answer back.
€200 divided by 0.80 is $250.
change it back: €200 ÷ 0.80 = 250
That is what we started with.
So the answer is right!
$250 — what we started with
Let's look back.
First: write the rate.
Then: multiply by the rate.
Last: check.
Answer
Careful: dollars → euros: × the rate