Let n = number of nickels, and p = number of pennies.
The number of coins is 25, so we get this equation.
n + p = 25
The value of the coins is 0.05 per nickel, and 0.01 per penny.
0.05n + 0.01p = 0.73
Now you have a system of equations.
n + p = 25
0.05n + 0.01p = 0.73
Solve the first equation for n:
n = 25 - p
Now substitute into the second equation.
0.05(25 - p) + 0.01p = 0.73
1.25 - 0.05p + 0.01p = 0.73
-0.04p = -0.52
p = 13
There were 13 pennies.
Now we substitute 13 for p in n + p = 25 to find out the number of nickels.
n + 13 = 25
n = 12
There are 13 pennies and 12 nickels.
Check: 13 pennies and 12 nickels does total 25 coins.
13 * 0.01 + 12 * 0.05 = 0.13 + 0.60 = 0.73
The value is $0.73.
Our answer is correct.
There's two ways to do this.
The first way:
Work out the amount of sugar needed to make one cake, and then multiply that by 7.
30 grams ÷ 4 cakes = 7.5 grams for 1 cake.
7.5 grams × 7 cakes = 52.5 grams for 7 cakes.
The second way:
Work out the ratio of sugar:cake by doing 7 ÷ 4, and then multiplying that value by 30.
7 cakes ÷ 4 cakes = 1.75
1.75 × 30 grams = 52.5 grams for 7 cakes.
Either way, the answer is 52.5 grams.
