The answer depends on the country (or region) whose currency you are working with. For example, the US has a 25 cent coin but not a 20 cent coin. The Eurozone has a 20 cent but not a 25 cent. Some countries have no coins smaller than 10 minor units.
Since you have not specified which country/region you are interested in, it is not possible to provide a more useful answer.
100x1p coins make a pound..
3 quarters 3 nickels and 10 pennies 25X3=75 5X3=15 1X10=10 75+15+10=100
To make 55 cents with 15 coins you will use 10 pennies, 1 quarter, and 4 nickles.
You can't make fractions of cents.
15
100x1p coins make a pound..
3 quarters 3 nickels and 10 pennies 25X3=75 5X3=15 1X10=10 75+15+10=100
Easy. Use 100 5-cent coins.
To make 55 cents with 15 coins you will use 10 pennies, 1 quarter, and 4 nickles.
12 x 100/80 ie 15%
To make up 100 grams using Australian coins, you could use ten 10-cent coins, which each weigh 5.65 grams, totaling 56.5 grams. Alternatively, you could use four 20-cent coins (each weighing 11.34 grams), totaling 45.36 grams, and then add two 50-cent coins (each weighing 15 grams) to reach 100 grams. Various combinations of coins can achieve this weight, but these examples illustrate a couple of possibilities.
You can't make fractions of cents.
15
The US Mint did not make any 100 dollar coins in 1959.
Fifteen 50p coins.
Five dimes and ten nickels.
0.15 = 15/100