Question

If 3 pens cost 45, what is the cost of 10 pens?

• A. 100
• B. 120
• C. 150
• D. 180

Hint:

Proportionality problems require establishing the unit rate first. $3:45$ implies a ratio of $1:15$. Therefore, $10$ pens correspond to $10 \times 15 = 150$.

Answer 1

The Correct Option is C

First, we find the cost of a single pen (unit cost).
Cost of 1 pen $= \frac{\text{Total Cost}}{\text{Quantity}} = \frac{45}{3}$.
Cost of 1 pen $= 15$.
Now, calculate the cost of 10 pens.
Cost of 10 pens $= 10 \times 15$.
Cost of 10 pens $= 150$.