A box is filled with pennies, nickels, and dimes in a ratio of 2:3:4. If the total number of coins in the box is 1620, how many pennies are in the box

We could say that the number of pennies is 2x, nickels are 3x, and dimes are 4x. Adding all of them together, we get 2x+3x+4x=9x. We also know that 9x=1620 because the total amount of coins is 1620. Dividing by 9 on both sides we get x=180.

Pennies equal 2x = 2*180=360