So we need to write some equations to solve for the amount of nickels and pennies, which represent our two variables. We know the total amount of nickels and pennies equals $1.42, so we say 0.01P + 0.05N = 1.42. We also know the number of pennies is 38 less than 4 times the number of nickels, so we say P + 38 = 4N. So divide 4 from both sides to get N = 0.25P + 9.5. Plug that into the other equation to get 0.01P + 0.05(0.25P + 9.5) = 1.42. Distribute to get 0.01P + 0.0125P + 0.475 = 1.42. Subtract 0.475 and add the pennies together to get 0.0225P = 0.945. Divide 0.0225 from both sides and P = 42. So there are 42 pennies total in the coin bank.
Apr 28th, 2015
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