Marbles come in 2 sizes: 1-inch diameter and 2-inch diameter. The one-inch diameter marbles cost 30 cents less than the two-inch marbles. Rochelle buys 25 one-inch marbles for her science project and spends exactly $10. Find the cost of a two-inch marble.

Answer 1

Let's assume that the cost of a two-inch marble is $x
The cost of a one-inch marble is $x-30 cents.
Since Rochelle bought 25 one-inch marbles, she spent 25*(x-30) cents which is equal to $10.
So 25*(x-30)=10*100 cents
25x-750=1000
25x=1000+750
25x=1750
x=1750/25
x=$<<70=70>>70
The cost of a two-inch marble is $70. Answer: \boxed{70}.