average cost of 8 pens and 5 pencil is 25.and average cost of 4 pens and 7 pencils is 21.find out total cost of 18 pens and 18 pencils is.
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average cost of 8 pens and 5 pencils is 25
so total cost here (8+5)*25=325 rs
total cost of 4pens and 7 pencils is (4+7)*21=231 Rs
let cost of 1 pen is x rs and cost of 1 pencil is y rs
so 8x+5y=325..... (1)
and 4x+7y=231.... (2)
solving (1) and (2)
x=274/18 and y=560/18
so cost of 18 pens and 18 pencils is 18x+18y=274+560=834 rs
so total cost here (8+5)*25=325 rs
total cost of 4pens and 7 pencils is (4+7)*21=231 Rs
let cost of 1 pen is x rs and cost of 1 pencil is y rs
so 8x+5y=325..... (1)
and 4x+7y=231.... (2)
solving (1) and (2)
x=274/18 and y=560/18
so cost of 18 pens and 18 pencils is 18x+18y=274+560=834 rs
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