A basic calculator in Quantitative Reasoning
ETS provides an on-screen calculator for Quantitative Reasoning and recommends using it for tedious operations. Its official page and POWERPREP let you explore the actual interface. This article does not reproduce its buttons and is not a calculator simulator.
First decide whether you need a complete numerical value. To compare two fractions, simplifying or cross-multiplying may be enough. To calculate an amount from several decimals, the tool may reduce the calculation load. In either case, keep an independent estimate to catch an inconsistent input.
Case 1: mental math is straightforward
The following example compares two ways to find the same quantity. Which is better depends on your comfort level; there is no universal speed requirement.
What is 12.5 percent of 240?
Enter your answer before viewing the review.
The solution, step by step
30.
The method in action
- Without a calculator: 12.5% = 1/8, so 240/8 = 30. Recognizing this gives you a short, verifiable calculation.
- With a calculator: entering 0.125 × 240 also gives 30; the interface uses a decimal point. The risk is entering 12.5 × 240, which omits division by 100.
- Estimate: one-eighth of 240 should be greater than 10% of 240, or 24, and less than one-quarter, or 60. The result of 30 is reasonable.
Case 2: let the tool do the work
When the model is clear and the calculation itself is not instructive, it is reasonable to delegate the operation. First write one line explaining what the result represents.
A supplier charges $18.75 per unit. What is the total cost of 64 units, excluding any other charges?
Enter your answer before viewing the review.
The solution, step by step
1 200 dollars.
The method in action
- With a calculator: entering 18.75 × 64 gives 1,200. The model is unit cost × quantity.
- Without a calculator: 18.75 × 8 = 150, then 150 × 8 = 1,200. This approach works but may be less obvious if decimal fractions slow you down.
- An estimate of 20 × 64 = 1,280 gives a nearby upper bound. A display of 12,000 or 120 would indicate an input or decimal-place error.
Case 3: calculation can obscure proof
For a comparison, a rounded decimal may hide the difference you are looking for. Keep exact expressions as long as possible.
Quantity A: 17/19. Quantity B: 18/20. Which quantity is greater?
Enter your answer before viewing the review.
The solution, step by step
Quantity B.
The method in action
- Without a calculator: the denominators are positive, so compare 17 × 20 = 340 with 18 × 19 = 342. The second fraction is greater.
- With a calculator: 17/19 is about 0.8947; 18/20 is 0.9. The tool confirms the relationship, as long as you do not round the first value too early.
- Two numbers that both display as 0.9 after your own rounding are not proof of equality. Cross-multiplication gives an exact comparison here.
The pitfall
The pitfall to avoid
Treating a displayed value as validation of your reasoning is a mistake. The calculator faithfully evaluates an incorrect expression. An average speed calculated as the simple average of two speeds may produce a neat decimal and still be wrong.
Learn the interface before a simulation
The calculator follows the order of operations: 1 + 2 × 4 equals 9; (1 + 2) × 4 equals 12. Parentheses let you specify the intended grouping. Its memory has one slot, with recall, clear, and memory-add keys. Practice using them in POWERPREP before a simulation.
Transfer Display moves the displayed value to the answer field for a one-field Numeric Entry question. Then check the units, any conversion to a percentage, and requested rounding; the transfer does not decide these for you. Without a rounding instruction, ETS expects an exact answer; do not replace an exact fraction with a truncated decimal.
During a practice session, note when you use the calculator and what it helps with. If you use it to avoid a basic fraction you do not yet understand, review that concept. If it performs a tedious division after you have chosen the right model, it is useful. The goal is to have two reliable approaches, not to ban either one.
Model, estimate, calculate, check
Before entering anything, identify the calculation and its approximate scale. Afterward, check the sign and units, then answer exactly what was asked: an area, percentage, or relationship. An intermediate result is not the answer just because it is the last number displayed.
During review, compare your solution with a shorter one when available. Keep the approach you can explain confidently. These exercises establish neither an official frequency of calculations nor guaranteed time savings; they show decisions you can test on your own practice sets.
Key takeaways
- Decide what needs to be calculated before entering it.
- Make an independent estimate to check the display.
- An exact proof may be shorter than a decimal.