Answer:
40 mph.
Step-by-step explanation:
Suppose grandma's house is 30 miles away (any distance would do but 30 is convenient).
Speed = distance / time
time = distance / speed
Time to get there = 30/60 = 1/2 hour.
Time to get back = 30/30 = 1 hour
Average speed = total distance/ total time
= (30 + 30) / ( 1 + 1/2)
= 60 / 1.5
= 40 miles per hour.
You cannot take the average of the speeds directly
(60+ 30)/2 = 45 is not correct as you cannot average ratios ( speed is a ratio).
Answer:
60480
Step-by-step explanation:
This question has to do with permutations. A permutation is used to find the number of possible outcomes, assuming order matters. In this case, n=9 and r=6. This is written as 
which equals 
. Then, plug this into a calculator to get 60480.
<span>In order to add and subtract fractions, we must be able to find a <u>common denominator</u>.
The LCD, or least common denominator, is the LCM of the denominators. Once we've added, subtracted or multiplied fractions, we often have to simplify the fraction.
In order to do this, we divide the numerator and denominator by their GCF. This means we must be able to find the LCM and GCF in order to work with fractions.</span>
I don’t really understand for question 11 to 13
