Question 144965
1.  a.  Since every kilowatt-hour costs $0.07, you simply multiply the number of kw-hrs used by 0.07.  If you used {{{h}}} kw-hrs, then the variable cost would be {{{0.07h}}}.  Then you need to add the basic charge -- the amount you would have to pay even if you used no electricity at all that month, namely $12.00.  So the formula becomes:


{{{C[t]=0.07h+12.00}}} where {{{C[t]}}} is the total cost for the month.


1. b.  Simply substitute 1850 for {{{h}}} and do the arithmetic.


2. a.  Use the midpoint formulas.  Decide which of your points will be number 1 and which number 2 (It doesn't matter which) and then substitute the coordinate values into:


{{{x[m]=(x[1]+x[2])/2}}} and {{{y[m]=(y[1]+y[2])/2}}} to derive the coordinates of the mid-point, <big><b> ({{{x[m]}}},{{{y[m]}}}) </big></b>


2. b.  Use the distance formula.  Again, decide which point will be 1 and which will be 2.


{{{D=sqrt((x[1]-x[2])^2+(y[1]-y[2])^2)}}}.


Leave your answer in terms of the radical if the number is not a perfect square to get the exact answer.  You may want to see if you can simplify the radical by factoring out perfect squares from the radicand.  For example, {{{sqrt(8)=sqrt(4*2)=sqrt(4)*sqrt(2)=2sqrt(2)}}}


Use your calculator to get a numerical approximation of the square root and then round to three places as instructed.