Let me guess the answer is 8
You need to find the total distance and the total time. The total distance is two times the distance to school, 2d.s=d/t=>t=d/sWhere s is speed, d is distance and t is time. So the time taken to get to school is:d/s1and the time taken to get back is:d/s2so the total time is:d/s1+d/s2=d(1/s1+1/s2)So, as speed = distance/time, divide the total distance by the total time:2d/d(1/s1+1/s2)=2/(1/s1+1/s2)=2/(1/20+1/40)=80/3≈26.7km/hr
<span>Simplifying
3n + 9 = 7n + -15
9 + 3n = 7n + -15
9 + 3n = -15 + 7n
9 + 3n = -15 + 7n
9 + 3n + -7n = -15 + 7n + -7n
3n + -7n = -4n
9 + -4n = -15 + 7n + -7n
7n + -7n = 0
9 + -4n = -15 + 0
9 + -4n = -15
9 + -9 + -4n = -15 + -9
9 + -9 = 0
0 + -4n = -15 + -9
-4n = -15 + -9
-15 + -9 = -24
-4n = -24
Divide each side by -4
n = 6 </span>
Remember that
the formula to calculate the combination is equal to
nCr=n!/[r!(n-r)!]
in this problem
we have
n=4
r=3
substitute the given values
4C3=4!/[3!(4-3)!]
4C3=4!/[3!(1)!]
4C3=4*3!/3!
4C3=12
the answer is 12
For 2 scoops
we have
n=4
r=2
substitute
4C2=4!/{2!(4-2)!]
4C2=(4*3*2*1)/4
4C2=6
the answer is 6
