Pen, Pencil, and Rubber in a box are in proportion to 3:

Solution

Let the ratio of pen, pencil, and rubber in the box be 3x: 2x: x (since the ratio is given as 3:2:1). Let the value of a pen, pencil, and rubber be Rs. 3, Rs. 2, and Rs. 2, respectively. Then, the amount spent on the box can be calculated as: Amount spent = (value of a pen x 3x) + (value of a pencil x 2x) + Amount spent = (3 x 3x) + (2 x 2x) + (2 x x) [substituting the given Amount spent = 9x + 4x + 2x Amount spent = 15x It is given that the amount spent on the box is Rs. 840. So, we have: 15x = 840 x = 56 Therefore, the ratio of pen, pencil, and rubber in the box is 3x: 2x: x = 168:112:56.   So, the number of pens in the box is 168.