The total price would be $1.08! Hope this Helps :-)
To start to figure this problem out, we can first figure out how many more pages you read in an hour compared to your sister.
50 - 40 = 10, so you read 10 more pages in 1 hour.
Now we have to figure out how much more you would read in 1/2 an hour. Since 1/2 an hour is 1/2 of an hour, we can divide 10 by 2 to figure out how many more pages you read in an hour compared to your sister. 10 divided by 2 is 5, so you read 5 more pages every half hour.
This is the number of combinations of 2 from 23
23C2 = 23! / 2! 21!
A quick way to do this is 23*22 / 2 = 253
