To find the answer, you first should find out how long is 25% of the original battery life, 16 hours. To find this, you can divide 16 by 4, or multiply 16 by 0.25. Either works.
16/4=4.
So the new battery lasts 4 hours more than the old battery. Then, add this to the original length to find how long the new battery will last in total.
