20 note books, 100 pens and 50 pencils were bought for ₹3,500. If the average cost of a note book is ₹50 and that of a pencil is ₹10, find the average cost of a pen.
₹20
Cost of note books: \(20\times50 = 1000\). Cost of pencils: \(50\times10 = 500\).
Cost of 100 pens: \(3500-1000-500 = 2000\).
Average cost per pen: \(\dfrac{2000}{100} = 20\).
Hence, the average cost of a pen is ₹20.
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