The ruiz family is exchanging euros for us dollars the exchange rate is 1 euro equals 1,35261 usd since the ruiz family knows that usd are stated to the nearest hundredth of a dollar they used the conversation ratio

You have to multiply the number of dollars times the conversion ratio is used in this way.

If you use the nearest hundredth approximation of the conversion ratio you have to use 1.35 instead the real exchange ratio of 1.35261

So, if they change Eu 1 will receive $ 1.35 instead of $ 1.35261.

If they change Eu 10 will receive 10 × 1.35 = $ 13.5, instead of $13.5261

If they change Eu 100 will receive 100 × 1.35 = $ 135, instead of $135.5261

If they change Eu 1,000 will receive 1000 × 1.35 = $ 1350, instead of $ 1352.61

So, you see the lose is $ 2.61 per every 1000 Euros they change.