Distance = speed x time
Distance travelled by car A when car B started = 60 x 2 = 120 miles
Number of miles remaining at the time car B started = 400 - 120 = 280 miles.
At time of their meeting both cars has travelled a combined distance of 280 miles and has spent the same time.
Let t be the time they travelled together before they meet, then the sum of the distance travelled by car A and car B is 280miles.
60t + 80t = 280
140t = 280
t = 280/140 = 2 hours
After 2 hours car A has travelled a further 60 x 2 = 120 miles and car B has travelled 80 x 2 = 160 miles.
Total distance travelled be car A is 120 + 120 = 240 miles
Midpoint of the journey = 400/2 = 200 miles
Therefre, at the time they met, the were 40 miles from the midpoint and they are close to San Francisco.
It's B
Slope is negative, the other must be positive due to m1 x m2 = - 1
m1 = -2/5
The diagram shows a gradient of -2/5. So, the
reciprocal of this valve to make - 1 is 5/2 (which is the - 2/5 flipped upside down, but positive)
-2/5 x 5/2 = - 10/10 (or - 1)
Thus, the perpendicular line to this has a gradient of 5/2.
Hope this helps!
20: Let 
be the amount of money. If this amount is shared between 8 people, each person will get x/8 dollars. But there actually are 6 people, so everyone is getting x/6 dollars. We know that this difference results in 30 dollars more, so we have
Rearrange the left hand side as
And multiply both sides by 24 to get
21: Let 
and 
be the number of marbles owned by Mike and Judy, respectively. At the beginning, we have
If they both get 9 more marbles, Mike will have 
marbles, and Judy will have 
marbles. So, we have
Plug this value in the first equation and we have
And we deduce
So, the difference is
22: Let 
be the number of $10, $20 and $50 coupon, respectively. We're given:
![\begin{cases}x=2y+3\\z=\frac{1}{2}y\\x+y+z=38\end{cases} We can write the third equation by substituting the expressions for x and z: [tex]x+y+z=(2y+3)+y+\left(\dfrac{1}{2}y\right)=38](https://tex.z-dn.net/?f=%5Cbegin%7Bcases%7Dx%3D2y%2B3%5C%5Cz%3D%5Cfrac%7B1%7D%7B2%7Dy%5C%5Cx%2By%2Bz%3D38%5Cend%7Bcases%7D%0A%3C%2Fp%3E%3Cp%3EWe%20can%20write%20the%20third%20equation%20by%20substituting%20the%20expressions%20for%20x%20and%20z%3A%0A%3C%2Fp%3E%3Cp%3E%5Btex%5Dx%2By%2Bz%3D%282y%2B3%29%2By%2B%5Cleft%28%5Cdfrac%7B1%7D%7B2%7Dy%5Cright%29%3D38)
Rearrange as follows:
And now we can deduce the number of the other coupons:
So, the total value is
23: a) In order to find the first three terms of the sequence, you just need to plug n=1,2,3:
b) We have
c) 105 is a term of the sequence if and only if there exists an integer k such that
So, 105 is not a term of the sequence.
ACUTE ANGLE.
this is because the angle is less than 90 degree and greater than 0 degree
