Step by step
The question
Question: change $200 to euros, when $1 = €0.85.
$1 = €0.85. Change $200 to euros.
1 Write the rate
The rate says: 1 dollar is worth 0.85 euros.
$1 = €0.85
From dollars to euros, we multiply by 0.85.
Going back, we divide by 0.85.
dollars → euros: × 0.85
euros → dollars: ÷ 0.85
2 Multiply by the rate
Each dollar is worth €0.85.
200 dollars are worth 200 times as much.
$200 = 200 × €0.85
200 times 0.85 is €170.
= €170
To multiply decimals: first 200 times 85, as whole numbers.
That is 17000.
Then count the decimal places: 2.
200 × 85 = 17000
2 decimal places: 170
Careful!
Check the direction.
Dollars to euros: we multiply by the rate.
Careful: dollars → euros: × the rate
So $200 is €170.
3 Check
Let's check: change the answer back.
€170 divided by 0.85 is $200.
change it back: €170 ÷ 0.85 = 200
That is what we started with.
So the answer is right!
$200 — 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