SOLUTION: Please help me to solve the following equations: Solve each formula for the indicated variable: 18) I= E/R+r for R Please find the value of the indicated variable:

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Question 88386: Please help me to solve the following equations:
Solve each formula for the indicated variable:
18) I= E/R+r for R

Please find the value of the indicated variable:
Please show a complete solution to each problem.
36) Ride the peaks. Smith bicycled 45 miles going east from Durango, and Jones bicycled 70 miles. Jones averaged 5 miles per hour than smith, and his trip took one-half hour longer that Smith's. How fast was each one traveling?
Thank you so much for your assistance
Answer by ankor@dixie-net.com(22740) (Show Source):
You can put this solution on YOUR website!
solve each formula for the indicated variable:
:
Assume you mean:
I = for R
:
Multiply both sides by (R+r) and you have:
I(R+r) = E
:
Divide both sides by I and you have:
R + r =
:
Subtract r from both sides:
R = - r
:
:
36) Ride the peaks. Smith bicycled 45 miles going east from Durango, and Jones bicycled 70 miles. Jones averaged 5 miles per hour than smith, and his trip took one-half hour longer that Smith's. How fast was each one traveling?
:
Kind of a poorly worded problem, I interpret it to mean:
It took Jones a half hour longer to travel 70 mi than Smith to travel 45 mi
:
Let s = smith's speed
then
(s+5) = Jone's speed
:
Write a time equation;Time = Dist/time
:
Smith's 45 mi time + half hr = Jone's 70 mi time
+ =
:
Multiply equation by 2s(s+5) to get rid of the denominators, we have:
45*2(s+5) + s(s+5) = 70*2s
:
90s + 450 + s^2 + 5s = 140s
:
s^2 + 90s + 5s - 140s + 450 = 0
:
s^2 - 45s + 450 = 0; a quadratic equation
:
Factors to:
(s - 15)(s - 30) = 0
:
s = 15
and
s = 30
:
Check both solutions
s = 15, then j = 20
45/15 = 3 hr
70/20 = 3.5 hr
and
s = 30, j = 35
45/30 = 1.5 hrs
70/35 = 2.0 hr
:
Interesting that both solution work, isn't it?