The No-Calculator Challenge: Sharpening Your Mental Math Skills for the CPS HSAT

Of all the rules for the High School Admissions Test, one sends a particular shiver down the spine of many students: no calculators are allowed. In a world where we have a calculator in our pocket at all times, facing a math test without one can seem daunting.

But here’s a secret: the no-calculator rule is actually a clue. It tells you that the HSAT Math section is designed to be a test of your mathematical reasoning, not your ability to crunch complex numbers. The problems are built to be solved with your mind, and sharpening your mental math skills is the key to unlocking this challenge.

Think of this guide as your summer workout plan for building the mental math muscles you need for test day.

Why Mental Math is Your Superpower on the HSAT

  • Unbeatable Speed: Every time you perform a calculation in your head instead of on paper, you save precious seconds. Over an entire section, this saved time adds up, giving you more opportunity to tackle tough problems or double-check your work.

  • Enhanced Accuracy: Strong number sense helps you recognize when an answer just "looks wrong." If you multiply 19 by 5 and get 950, your mental math skills will immediately flag that the answer should be closer to 100, helping you catch careless errors.

  • Increased Confidence: Fluency with numbers reduces anxiety. When you're not struggling with basic calculations, you can dedicate all your brainpower to the actual problem-solving, which is what the test truly measures.

Your Mental Math Workout Plan

Incorporate these drills into your study routine to see rapid improvement.

1. Percentage Shortcuts Instead of complex multiplication, use the power of 10%.

  • To find 10% of any number, just move the decimal one place to the left (e.g., 10% of 350 is 35.0).

  • To find 5%, find 10% and cut it in half (5% of 350 is 17.5).

  • To find 20%, find 10% and double it (20% of 350 is 70).

  • To find 15%, find 10% and 5%, then add them together (15% of 350 is 35 + 17.5 = 52.5).

2. The Art of Estimation On a multiple-choice test, you often don't need the exact answer. You can round numbers to get close enough to eliminate wrong choices.

  • Problem: What is 24.7 x 8.1?

  • Estimation: This is very close to 25 x 8, which is 200. Look for the answer choice nearest to 200.

3. Master Your Core Facts Spend time memorizing your multiplication tables up to 20x20 and the most common fraction-to-decimal conversions (e.g., 1/4 = 0.25, 1/8 = 0.125, 3/4 = 0.75).

Putting Your Skills to the Test

These drills build your foundational skills, but you must apply them under pressure to be ready for test day. This is the entire purpose of practice testing. When you take timed CPS HSAT Practice Tests, you are forced to perform these mental calculations under the same stress as the real exam. You'll quickly see where your mental math is fast and where it slows you down, showing you exactly which drills you need to focus on.

Remember, "no calculator" doesn't mean you can't write anything down. You should use your scrap paper to jot down the results of your mental calculations as you work through a multi-step problem. This is a key strategy we discuss in our main HSAT Math Section guide.

View the no-calculator rule as a challenge to be conquered, not a barrier. Start your mental math workout today, and by test day, you'll be solving problems with speed and confidence while others are still wishing for a calculator that isn't there.