Strategy guides › Number Rush
Number Rush: what the questions are made of, and how to go faster
Twenty seconds left, thirty points on the board, and the screen says 12 × 13. Two of the four options end in 6. Your brain starts to multiply properly, digit by digit, and by the time you have it, three seconds are gone. There was a faster way: one digit to throw out the near misses, one rough estimate to pick between the rest.
Number Rush gives you sixty seconds. A right answer scores a point; a wrong one takes two seconds off the clock. Everything below comes from reading the code that writes the questions, so you know exactly what is coming.
What you will be asked
Every question is one of four kinds, picked at random each time: addition 35% of the time, subtraction 25%, multiplication 25% and division 15%. How big the numbers get depends on a level, and the level is simple. It starts at 0 on Easy, 1 on Normal and 3 on Hard, and goes up by one for every five correct answers. Your streak does not change it, and neither do mistakes. A score of 20 on Normal means your last questions were at level 5.
| Level | Addition: each number | Subtraction: the first number | Multiplication and division: each factor |
|---|---|---|---|
| 0 | 2–10 | 5–20 | 2–6 |
| 1 | 2–14 | 5–25 | 2–7 |
| 2 | 2–18 | 5–30 | 2–8 |
| 3 | 2–22 | 5–35 | 2–9 |
| 4 | 2–26 | 5–40 | 2–10 |
| 5 | 2–30 | 5–45 | 2–11 |
| 6 | 2–34 | 5–50 | 2–12 |
| 7 | 2–38 | 5–55 | 2–13 |
| 8 | 2–42 | 5–60 | 2–14 |
In a subtraction the second number is never bigger than the first, so answers are never negative (though 0 can happen). A division is always a multiplication turned round: the game picks a divisor and an answer from the same range as the factors, multiplies them, and shows you the product. So 84 ÷ 12 only appears once 12 is in the factor range, from level 6.
Two things follow. The times tables you need stop at 6 on level 0 and only reach 12 × 12 at level 6, which on Normal means a score of 25. And addition is the most common question at every level, with a carry in roughly four or five of every ten sums.
Last digit first, then size
The four options always form the same shape: two pairs, ten apart. If the answer is 156, the options might be 141, 146, 151 and 156, or 156, 159, 166 and 169. Exactly one wrong option is the answer’s twin: it is 10 higher or 10 lower, so it ends in the same digit. The other two end in a different digit, and they are each other’s twins. In 200,000 generated questions per level, that held every time. Where the answer sits in the pattern is picked at random, except that no option may go below zero.
So answer in two steps. First, work out the last digit: that throws out one pair and leaves two options exactly 10 apart. Second, decide between those two by size. Because they are 10 apart, a rough estimate is enough: when we fed our simulation an estimate that was off by up to 4 either way, the last digit plus that estimate picked the right option every time.
The last digit is a single-digit fact you already know. For addition, add the last digits: 27 + 38 ends in 5, because 7 + 8 = 15. For subtraction, borrow if you must: 52 − 17 ends in 5, because 12 − 7 = 5. For multiplication, multiply them: 13 × 12 ends in 6, because 3 × 2 = 6.
The size is the tens, and it only needs to be right to within a few. 27 + 38 is “twenty plus thirty, plus a carry”, so sixty-something: 65. For 52 − 17, fifty minus twenty is thirty, the borrow takes it into the thirties: 35. Watch the carry and the borrow, because a missed carry is exactly 10 out, which is exactly the twin.
Shortcuts for the higher levels
From level 7 the factors reach 13. Learn the 11, 12 and 13 rows as “ten times plus a bit”: 12 × 7 is 70 + 14, and 13 × 6 is 60 + 18. That split is also the estimate: 13 × 12 is 120 plus 36, which tells you both the last digit and the size in one go.
Division answers are small, never more than the top of the factor range, so a twin 10 away usually looks wrong at a glance. Turn the division into “what times the divisor gives this?” and use your tables. The last digit still helps as a check: in 84 ÷ 12, the answer times 12 must end in 4, so it ends in 2 or 7; 2 × 12 is far too small, so it is 7.
For subtractions where the second number is small, like 40 − 3, count back rather than computing; the game asks plenty of these, because the second number can be anything from 1 up to the first.
Never guess
Two seconds per mistake is expensive. If you tap at random among four options and keep trying, you will on average hit 1.5 wrong options before the right one, which costs three seconds of penalty on top of the taps. Even after the last digit, a blind pick between the two twins is wrong about half the time; a one-second estimate is cheaper. Wrong answers also reset your streak counter, though the level, and with it the difficulty, keeps climbing with your score either way.
Practice
There is no special puzzle to load here: every round is fresh. Play one round on Normal in two steps for every sum, last digit first and then the size, and see how your score compares with your best.
Last digit to clear the noise, tens to make the call.
