Operations and Algebraic Thinking: Solving Word Problems with Multiplicative Comparison (CCSS.4.OA.2)
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4th Grade Math › Operations and Algebraic Thinking: Solving Word Problems with Multiplicative Comparison (CCSS.4.OA.2)
Mia has 5 books. Her brother has 3 times as many books as Mia. Let $b$ be the number of books her brother has. Which equation represents this situation?
$b = 5 + 3$
$3 = 5b$
$b = 3 \times 5$
$b = 5 \div 3$
Explanation
Three times as many means multiply: $b = 3 \times 5$. Adding 5 + 3 or reversing to $3 = 5b$ does not match the comparison.
A jar holds 24 marbles. This is 4 times as many marbles as in a small cup. Let $c$ be the number of marbles in the small cup. Which equation could you use to find $c$?
$c = 24 \div 4$
$c = 24 - 4$
$c = 24 \times 4$
$4 = 24 \times c$
Explanation
If 24 is 4 times the cup, then $24 = 4 \times c$, so $c = 24 \div 4 = 6$. Subtraction or multiplying 24 by 4 does not match the multiplicative comparison.
Sam has 3 marbles. Jose has 4 times as many marbles as Sam. How many marbles does Jose have?
7
12
3
4
Explanation
This is a multiplicative comparison: 4 times as many means 3 × 4 = 12, not 3 + 4 = 7.
A shelter has 6 kittens. It has 2 times as many puppies as kittens. How many puppies does the shelter have?
8
3
12
6
Explanation
Two times as many means multiply: 6 × 2 = 12. Adding 6 + 2 = 8 or dividing 6 ÷ 2 = 3 are additive/division mistakes.