A store sells batteries in packets of 6 or 10. It has a stock of 25 packets containing a total of 186 batteries. How many of these are 10-battery packets?

Question

anonymous · Answer

s = 6 pack batteries
t = 10 pack batteries

s + t = 25 -->s = 25 - t
6s + 10t = 186

now sub 25 - t in for s in the 2nd equation
6(25 - t) + 10t = 186
150 - 6t + 10t = 186
150 + 4t = 186
4t = 186 - 150
4t = 36
t = 9

s + t = 25
s + 9 = 25
s = 25 - 9
s = 16

check...
6s + 10t = 186
6(16) + 10(9) = 186
96 + 90 = 186
186 = 186 (correct)

There were 9 ten pack batteries = 90 batteries
There were 16 six pack batteries = 96 batteries
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total : 25 packs of batteries = 186 batteries