You computed 2/3 + 1/5 on the home screen and got 0.8666666667. Good luck submitting that on a worksheet.
The keystroke
Immediately after the answer appears, press math → 1:►Frac → enter. The decimal converts to its exact fraction representation. You'll see 13/15.
►Frac works on any recent answer that has a simple rational representation. For irrational numbers (√2, π, e), you'll get an ERR:DOMAIN or the calculator will leave the decimal alone.
Inline on any expression
You don't have to wait for a stored answer. Type the whole expression and stick ►Frac at the end before pressing enter:
2/3 + 1/5 ►Frac
Output: 13/15.
The inverse: MATH > Dec
math → 2:►Dec goes the other direction — converts a fraction back to a decimal. Useful when a homework problem gives you a fraction and you need the decimal to plug into another formula.
The n/d and U n/d templates
On the CE, alpha + y= opens the template menu. Two of them are fraction-specific:
- n/d — a proper or improper fraction. Type numerator, arrow down, type denominator.
- U n/d — a mixed number. Type whole number, arrow right, type fraction.
These templates render the fraction vertically and let you type it naturally. The calculator treats the result as exact.
Converting between improper and mixed
math → B:n/d<>Un/d (might be C: depending on firmware) toggles a displayed fraction between improper (13/5) and mixed (2 3/5).
Why this matters
Teachers mark answers wrong for 0.666... when the correct answer is 2/3, even if they're numerically equal. Most students don't know ►Frac exists and lose points on arithmetic they did correctly.
Gotcha
►Frac silently fails on decimals that aren't simple rationals — anything beyond about 10 decimal places. If you got your decimal by dividing an irrational, ►Frac won't reverse it. You'd need to keep symbolic terms in the first place.