Arif bought 17 pens of three colors - black, green and red which cost Tk 5, Tk 10 and Tk 25 each. The total amount that Arif paid was Tk 205. If Arif bought twice as many green pens as red pens, how many black pens did he buy?
Explanation: ধরি, red pen কিনে x টি এবং black pen কিনে y টি। সুতরাং green pen কিনে 2x টি। \(x+y+2x=17\) or, \(3x+y=17...(i)\) এবং \(5y+20x+25x=205\) Or, \(5y+45x=205...(ii)\). \((ii)-(i) \times 5 \implies 30x=120\). Or, \(x=4 \implies 3 \times 4+y=17\). Or, \(y=5\). সঠিক Answer (B)
