Mitchell is a big coffee fan, so he always takes care of coffee brewing at the office. Normally he uses 100grams of Robusta coffee to prepare 10 cups of coffee. His friend brings him a packet of Arabica coffee and tells him that he should use 20% more than usual when brewing Arabica coffee.
How many grams of coffee should he use to make a 15-cup pot of Arabica coffee?
He uses 100 grams / 10 cups =10 grams per cup of Robusta coffee.
To make 15 cups of Robusta, he will need: 15/10 x 100 = 150 grams.
But for Arabica coffee, he will need:150 grams x 1.20 =180 grams.
So that: 180 grams / 15 cups =12 grams per cup of Arabica coffee.
And 12 grams per cup of Arabica is:12 / 10 =1.20 - 1 x 100 = 20% more than Robusta coffee.