SOLUTION: 7 audio cassettes and 3 video cassettes cost rs 1110,while 5 audio cassettes and 4 video cassettes cost rs 1350 find the cost of an audio cassette and a video casette
Question 445895: 7 audio cassettes and 3 video cassettes cost rs 1110,while 5 audio cassettes and 4 video cassettes cost rs 1350 find the cost of an audio cassette and a video casette Found 3 solutions by mananth, ikleyn, josgarithmetic:Answer by mananth(16949) (Show Source):
You can put this solution on YOUR website! Video--- x Cost
Audio=== y Cost
3x+7y=1100 .............1
4x+5y=1350 .............2
Eliminate y
multiply (1)by -5
Multiply (2) by 7
-15x-35y=-5500
28x+35y =9450
Add the two equations
13x=3950
/13
x= Rs.303.85 Cost of Video
plug value of x in (1)
3x+7y=1100
911.54 +7y=1100
7 y = 1100 -911.54
7 y = 188.46
y =Rs.26.92 Audio
You can put this solution on YOUR website! .
7 audio cassettes and 3 video cassettes cost rs 1110,while 5 audio cassettes and 4 video cassettes cost rs 1350
find the cost of an audio cassette and a video cassette
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In the post by @mananth the solution is incorrect, since equations are written incorrectly.
I came to do the job accurately.
Audio --- x Cost
Video --- y Cost
Equations
7x + 3y = 1110 (1)
5x + 4y = 1350 (2)
I will solve using the determinant method (= Cramer's method),
sinse it is easier to write (no need to write excessive words).
D (the determinant) is 7*4 - 5*3 = 28 - 15 = 13.
Dx (the determinant for x) is 1110*4 - 1350*3 = 390.
Dy (the determinant for y) is 7*1350 - 5*1110 = 3900.
Hence, x = Dx/D = 390/13 = 30; y = Dy/D = 3900/13 = 300.
ANSWER. Audio-cassette costs rs 30; video-cassette costs rs 300.
CHECK. First equation, left side is 7*30 + 3*300 = 1110. ! correct !
Second equation, left side is 5*30 + 4*300 = 1350. ! correct !
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