ProblemSum

Unlimited Singapore-style math word problems, every one worked step by step. Written for the exam that ends elementary school in Singapore — and for any child of 10 to 13 who wants a real challenge.

Fractions, ratios, percentages, algebra, averages, rates, area and volume, and more. Not geometry from a figure, charts or patterns drawn as shapes — those are read off a picture, and this app writes word problems.

No account. No subscription. No internet connection. Pay once and it's yours.

NOT A WORKBOOK THAT RUNS OUT
Most practice apps ship a fixed set of questions: work through them twice and your child is remembering answers instead of solving problems. ProblemSum has no such list. Every question is written the moment you ask for it, with its own names and numbers, and the solution follows those numbers — so there is no last page to reach.

ROOM TO WORK IT OUT
A scratch pad sits next to the question on iPad and Mac, and on an iPhone turned sideways; held upright, it slides up from below. Draw the model with a finger or Apple Pencil, or type the math. It never calculates: the first paper of Singapore's exam allows no calculator.

WORKED THE WAY SINGAPORE TEACHES
Tap Check Answer and the full solution opens, one tap from your own work. Most solutions start by naming the strategy Singapore students learn for that kind of problem — draw a model, before and after, work backward, make a supposition, guess and check — then show every line, with a check at the end. Most questions also show a second way to solve it; the rest point out the trap the question sets.

WHY SINGAPORE
In TIMSS, the international math study, Singapore's 4th graders came first in 2015, 2019 and 2023. In the OECD's PISA, taken by 15-year-olds, it has finished first or second in math in every round since 2009. Its methods — above all the bar model — are now used in classrooms and homeschools across the US.

WHO IT'S FOR
The questions are set at the level of that exam, Singapore's PSLE. That suits strong 5th graders and most 6th and 7th graders, and it works alongside any curriculum, at school or in a homeschool. Money is in dollars and cents, and every measure is metric.

BAR MODELS, DRAWN PROPERLY
Bars are drawn to scale with their units marked, the part that changes shaded, and brackets showing what's left. The rest is laid out the way it would be on paper: fractions stacked, ratios and money in their proper forms, and units carried through every line.

WHAT IT COVERS, AND WHAT IT DOESN'T
Fractions and ratios run deepest, then area and volume, percentages and whole numbers, then algebra, averages and rates, then decimals and measurement — with money, ages, time, discounts and sales tax running through them.
What it doesn't do: geometry from a figure, charts and graphs, or patterns drawn as shapes. Those are read off a diagram rather than a paragraph, so a word-problem generator can't write them. The Info tab lists both sides of that line.

ANSWER IT THE WAY YOU THINK OF IT
$4.50 or 4.50. Three-quarters as 3/4 or 0.75. A time as 1:45 p.m., 1.45 p.m. or 1345. 120 cm³ or just 120. A right answer is never marked wrong for its punctuation.

COME BACK TO WHAT YOU'VE DONE
Recent questions stay on the device with your answers, marked right or wrong, your work and the full solution, and you can step through them one by one.

ONE APP, EVERY LEARNER
A profile for each child, each keeping its own score, so siblings can share an iPad without sharing a total.

IPHONE, IPAD AND MAC
One purchase covers all three. The screen rearranges itself as it changes shape — an iPhone turned sideways, an iPhone Duo opened — and nothing written is lost. With a keyboard, Command-N gives the next question and Command-Return checks your answer.

WORKS ANYWHERE, TELLS NO ONE
ProblemSum makes no network connections at all. No analytics, no ads, no data collection — everything is generated on the device and stays there.

Spotted a mistake? Tell us at hello@problemsum.com.