Gilda sister has to swim 6.5 miles to use the same number of calories Gilda used during the marathon
Solution:
Given, Swimming
of a mile uses about the same number of calories as running 1 mile.
Gilda ran 26- mile marathon.
We have to find about how far would her sister have to swim to use the same number of calories Gilda used during the marathon
Now, according to given information,

Hence, gilda sister has to swim 6.5 miles.