# Math Help - midpoint, gradient and worded question

1. ## midpoint, gradient and worded question

please help and show working out

1. The midpoint of the line joining (k,2h) and (9k,6h+2) is (20,-11). Find k and h.

2. A factory produces 25 components at a cost of $830, and on another run produces 35 components at a cost of$1050. Find an expression relating the cost (C) to the number of components (n) produced, assuming a linear relationship.

3. ImageShack - Hosting :: mathxw9.jpg
I'm sorry it is upside down

2. the 2 make (x,y) and y=mx+n (linear) and just find ..

edit
answer y=22x+28 where cost = y and n =x , C=22n+28

3. Hello,

Originally Posted by poniekid
please help
Yes

and show working out
No

1. The midpoint of the line joining (k,2h) and (9k,6h+2) is (20,-11). Find k and h.
Well, the coordinates of a midpoint between two points (a,b) and (c,d) is $(\frac{a+c}{2} ; \frac{b+d}{2})$.

So here you'll have 2 equations to solve for k and h.

Just to guide you, the first one will be :

$\frac{9k+k}{2}=20$