The cost of one pen is ₹42.25. Find the cost of one dozen such pens.

Given:

Cost of 1 pen = ₹42.25

Number of pens = 1 dozen = 12 pens

The cost of 1 dozen pens = (Cost of 1 pen) x (Number of pens)

Substituting the values in above, we get:

The cost of 1 dozen pens = ₹42.25 x 12

Sum of the decimal places in given decimals = 2 + 0 = 2

So, the product contains 2 places of decimal.

$\begin{matrix} & & 4 & 2 & 2 & 5 \ \times & & & & 1 & 2 \ \hline & & 8 & 4 & 5 & 0 \ & 4 & 2 & 2 & 5 & \times \ \hline & \bold{5} & \bold{0} & \bold{7} & \bold{0} & \bold{0} \end{matrix}$

∴ ₹42.25 × 12 = ₹507.00 = ₹507

Hence, the cost of one dozen pens = ₹507