A cookie recipe calls for 1 1/4 cups of flour. If Erin wants to make a double recipe, how many cups of flour will she need?
If the original recipe calls for 1 1/4 cups of flour, then to make a double recipe, Erin would need twice that amount.
1 1/4 cups is the same as 1 + 1/4 cups.
To calculate the double amount, you multiply each part by 2:
1 cup doubled is 2 cups,
1/4 cup doubled is 1/2 cup.
So, Erin would need 2 cups + 1/2 cup = 2 1/2 cups of flour for a double recipe.