John saved 20c and 50c coins. When he reached 100 coins the amount totalled $40.40.What percentage of the coins were 50 cent coins?

Let's denote the number of 20c coins as x and the number of 50c coins as y.

From the problem, we know two things:

1. John has a total of 100 coins, so x + y = 100.
2. The total value of all the coins is $40.40, or 4040c. Since each 20c coin is worth 20c and each 50c coin is worth 50c, we can also write 20x + 50y = 4040.

Now we have a system of two equations, and we can solve it step by step:

Step 1: Multiply the first equation by 20 to make the coefficients of x the same in both equations: 20x + 20y = 2000.

Step 2: Subtract the first equation from the second to find the value of y: 30y = 2040, so y = 2040 / 30 = 68.

Step 3: Substitute y = 68 into the first equation to find the value of x: x + 68 = 100, so x = 100 - 68 = 32.

So, John has 32 20c coins and 68 50c coins.

To find the percentage of the coins that were 50 cent coins, we divide the number of 50c coins by the total number of coins and multiply by 100%: (68 / 100) * 100% = 68%.