6 pencils cost ₹30 and 12 pens cost ₹120. What is the average cost of 50 pencils and 50 pens?
6 pencils cost ₹30.
Cost of one pencil = $$\frac{30}{6}$$
= ₹5
12 pens cost ₹120.
Cost of one pen = $$\frac{120}{12}$$
= ₹10
Average cost of 50 pencils and 50 pens = $$\frac{50\times\ 5+50\times10}{50+50}$$
= $$\frac{250+500}{100}$$
= $$\frac{750}{100}$$
= 7.5
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