Marbles come in two sizes one-inch diameter and two-inch diameter the one inch diameter marbles cost 30 cents less than the 2 inch marbles Rochelle buys 25 1 inch marbles for her science projects and spends exactly $10 find the cost of a 2 inch marble
Let's assume the cost of a one-inch diameter marble is x cents.
According to the given information, the cost of a two-inch diameter marble is x + 30 cents.
Rochelle buys 25 one-inch marbles, so the total cost of the one-inch marbles for her science projects is 25x cents.
We know that the total cost is $10, so we can set up the equation 25x = 1000 (since 1 dollar is 100 cents).
Solving this equation for x, we get x = 1000/25 = 40 cents.
Therefore, the cost of a two-inch diameter marble is x + 30 = 40 + 30 = <<40+30=70>>70 cents. Answer: \boxed{70}.