Question

There are five rounds in a game. Susan gets 9 gold coins in each round. Kim gets 7 silver coins in each round. One gold coin gives 10 points, and one silver gives 5 points. What is the difference between their points?

Answer 1

Let us calculate the number of points earned by Susan and Kim using associative property.
Let us recall this property:
Associative property states that the product of three or more numbers remains the same regardless of how the numbers are grouped.

Susan’s score
$\bullet$ Number of rounds $=5$
$\bullet$ Number of coins $=9$
$\bullet$ Points of one coin $=10$
Points earned = Number of coins $\times$ Number of rounds $\times$ Points of one coin
$\bullet$ Points earned$=(9\times 5)\times 10$
$\bullet$ Let’s use the associative property:
$=45\times 10$
$=450\text{points}$
Kim’s score
$\bullet$ Number of rounds $=5$
$\bullet$ Number of coins $=7$
$\bullet$ Points of one coin $=5$
$\bullet$ Points earned = Number of coins $\times$ Number of rounds $\times$ Points of one coin
$\bullet$ Points earned $=7\times (5\times 5)$
$\bullet$ Let’s use the associative property.
$\bullet$ Points earned $=7\times 25$
$=225\text{points}$
Let us find the difference in points:
$\bullet$ Difference $=450-225=225$

The difference between the points earned by Susan and Kim is 225 points.

Hence, A is the correct answer.