Apply Quantitative Logic
Reasoning with Numbers
Use logical reasoning to break down quantitative word scenarios and find the answer that must be true.
What is Quantitative Logic?
Quantitative logic means using reasoning instead of complex calculation. You read a number scenario, figure out the relationships between quantities, and decide what must be true.
Three Key Words to Watch
Picture the Comparison
The Core Rule
Translating Phrases to Math
| English Phrase | Math |
|---|---|
| "more than" / "increased by" | \( + \) |
| "less than" / "fewer" | \( - \) |
| "twice" / "double" | \( \times 2 \) |
| "half of" / "\( \tfrac{1}{2} \) of" | \( \times \tfrac{1}{2} \) |
| "is" / "equals" | \( = \) |
"Must Be" vs "Could Be"
How to Apply the Logic
Example 1: Simple Compare
Maria has 3 more stickers than Jon. Jon has more stickers than Kate. Who has the most?
Example 2: Chain Relations
A box of pens costs \( \$6 \). A box of markers costs twice as much as pens. How much do 2 boxes of markers cost?
Example 3: Must Be True
The average of three different whole numbers is \( 10 \). What must be true about the largest number?
Common Mistakes
Strategy Summary
| Do | Avoid | |
|---|---|---|
| Reading | Note relationships | Skim too fast |
| Translating | Use symbols | Reverse order |
| Reasoning | Test every case | Guess from one case |
| Effort | Compare smartly | Over-calculate |
Quick Recap
Now test your reasoning with five questions.
Question 1 of 5
Tom is taller than Sara. Sara is taller than Lee. Who is shortest?
Question 2 of 5
A pencil costs \( \$2 \). A pen costs \( \$3 \) more than a pencil. What is the cost of a pen?
Question 3 of 5
\( N \) is a whole number with \( N > 5 \). Which statement must be true?
Question 4 of 5
A box holds \( 12 \) eggs. A crate holds twice as many as a box. How many eggs are in \( 3 \) crates?
Question 5 of 5
The average of two different whole numbers is \( 8 \). Which must be true?
You've Got the Logic
Translate, chain, and test for what must be true. That's quantitative logic mastered.