How to Use the CAT On-Screen Calculator

What the calculator can and cannot do

The cat on screen calculator is a basic model, close to the Windows standard calculator many people last used years ago. It adds, subtracts, multiplies, and divides. It also has square root, reciprocal, and percent, plus five memory keys: MC, MR, MS, M+, and M-. That is the whole inventory. There are no logarithms, no trigonometry, and no powers, so a step you would do in one line on a phone takes two or three here. Planning for that, instead of discovering it mid-section, is most of the work.

Every button, one at a time

Speed comes later; first comes vocabulary. Here is what each key does:

• Digits and the decimal point enter one number. Each entry accepts at most 8 digits, and the display simply stops taking more.
• The four operators (+, -, ×, ÷) chain left to right. The top line of the display shows the expression built so far.
• = finishes the current operation and shows the result.
• C clears everything back to zero. Use it between questions, not just between calculations.
• The sign key (+/-) flips the current entry between positive and negative.
• √ returns the square root of the displayed entry.
• 1/x divides 1 by the displayed entry, which is quicker than a division whenever the number reduces to a clean reciprocal.
• % follows the Windows calculator's behavior: in 4800 + 8 %, the 8 means 8 percent of 4800, so equals gives 5184. In 4800 × 12 %, it means 12 percent as a plain multiplier, giving 576.
• Backspace deletes the last digit typed, which saves a full re-entry when the seventh digit goes in wrong.

The 8-digit entry limit

Eight digits per entry sounds generous until a number like 14,392,675 does not fit. The fix is to break the entry, not the calculation. Enter what fits, compute a partial result, store it with a memory key, and continue with the rest. The limit applies to what you type, not to results: a product can show more digits than eight. Practice long entries until you notice the cutoff on the spot instead of three keys later.

Memory keys: one step instead of starting over

The five memory keys carry an intermediate result across a gap, and they are the reason a basic calculator is workable at all:

• MS stores the value currently on the display.
• MR brings the stored value back.
• M+ adds the displayed value to memory and M- subtracts it.
• MC clears memory. A stale value from a previous question is a classic source of wrong answers, so clear it when a calculation ends.

A worked sequence: to take 12% of 4,800 and then 8% of the result, enter 4800 × 12 % =, which shows 576, press MS to hold it, then × 8 % = for 46.08. MR brings the first figure back whenever the question needs it. Nothing was retyped and nothing was scribbled on paper.

Clicking is the only input

The exam offers no keyboard, so every key is a mouse click. That makes the layout worth learning the way you would learn keyboard shortcuts. A candidate who has to search for the percent key loses a few seconds on every percentage question; across a 40-minute section, those seconds add up to minutes. Practicing on a cat calculator simulator that matches the exam layout key for key moves the key positions into your hand rather than your head. The argument in full is in why you need a CAT calculator for exam practice.

Common mistakes

• Pressing = twice, which repeats the last operation and quietly corrupts the result.
• Leaving a value in memory from an earlier question, then recalling the wrong number with MR.
• Typing a nine-digit entry, getting a truncated number, and noticing only when the answer looks strange.
• Using the calculator for arithmetic that is faster by hand, like 25% of 80. The machine is there for the heavy work, not for every step.

Whether the calculator is even allowed, and how the rules read, is covered separately in can you use a calculator in the CAT exam. Otherwise the cat exam calculator on this page is free, needs no sign-up, and matches the exam machine key for key. Run one memory-key sequence and you will know how ready you are.