SOLUTION: A group of 10 6- and 12- voltbatteries are wired in series as shown at the right. the sum of their voltages is 84 volts. How many of each type of battery are used?

Question 100651: A group of 10 6- and 12- voltbatteries are wired in series as shown at the right. the sum of their voltages is 84 volts. How many of each type of battery are used?
Answer by oberobic(2304) (Show Source): You can put this solution on YOUR website!
We have 10 batteries, so let's say the number of 6V batteries is x. That means the number of 12V batteries is 10 - x.
And we're told that 6x + 12(10-x) = 84 volts. 6x is the 6 volts per battery times x, which is the number of 6V batteries. Likewise 12(10-x) is the 12 volts per battery times the number of 12V batteries.
So, we have 6x + 120 - 12x = 84. Combining the x terms we have -6x + 120 = 84. Subtracting 120 from both sides, we have -6x = -36. Dividing by -6, we have x = 6.
That means the number of 6V batteries is 6, and the number of 12V batteries is 10-6=4.
ALWAYS check! 6*6=36 and 4*12=48, 36+48=84. Check.
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