0.4 miles
1.69 miles
3.0 miles
6.4 miles

.4 is the answer

Step-by-step explanation:

This is a right triangle problem.  We have one leg as .5 in length and the other leg as 1.2 in length.  The "straight" way to your grandma's house is the hypotenuse.  We need to find that length which will give us the distance straight from your house to their house if you didn't have to go out of your way to avoid the water.  The hypotenuse is found with Pythagorean's Theorem.  It will be filled in and solved as follows:

and c = 1.3

That's the straight distance.  You had to go out of your way to the tune of .5+1.2 which is 1.7 miles.  You figure out how much shorter it is taking the straight path by subtracting 1.7 - 1.3 which is .4

congruent segments

step-by-step explanation: