Maci is planning for the new school year and goes to the store to buy pens. She needs ten blue pens and 15 red pens. If a blue pen costs ten cents each and a red pen costs twice as much as the blue pen, how much money does Maci pay for the pens?
Maci pays 10 * $0.10 = $<T>multiply(10, 0.1)=1.0 for the blue pens.
Each red pen costs 2*$0.10 = $<T>multiply(2, 0.1)=0.2
She pays 15*$0.20 = $<T>multiply(15, 0.2)=3.0 for the red pens.
To buy all the pens she needs, Maci pays $3+$1= $<T>add(3, 1)=4
