Question

Cosmo has $7$ groups of $3$ balls to play with. Carla has $3$ groups of $7$ balls to play with. How many balls are there in total to play with?

• A. $42$ balls
• B. $21$ balls
• C. $20$ balls
• D. $10$ balls

Answer 1

The correct option is A $42$ balls

Number of balls Cosmo has $=7$ groups of $3$
$=7\times 3$
$=21$ balls
Number of balls Carla has $=3$ groups of $7$
$=3\times 7$
$=21$ balls
The total number of balls there are to play with $=21+21=42$

Notice that writing $3\times 7$ or $7\times 3$ made no difference to the answer. We had $21$ balls in each case. This is an interesting thing about multiplication.

Hence, option C is correct.