Quizzes
Fluency
Squares 1–32
Memorise n² for n = 1 through 32 — the foundation for Pythagoras, sqrt estimation, and variance.
Number bonds to 10
Pairs that sum to 10. The bedrock of carrying.
Number bonds to 100
Random pairs that sum to 100. Powers compensation, change-making, percentages.
×-tables 2–9
The full multiplication table without the trivial 1× and 10× rows.
Powers of 2 (1–4096)
Doubling chain. Powers binary intuition, log₂ estimation, capacity sense.
Powers of 3, 5, 7
Non-binary anchor primes. Powers compounding intuition.
Log₁₀ of 2, 3, 7
Three constants that bridge multiplication and order-of-magnitude estimation.
Fraction / decimal anchors
Unit fractions 1/2 through 1/12 plus 1/100. Powers benchmark-percentage moves.
Strategy
Compensation (add)
Round one addend to a friendlier number; subtract the same amount from the other so the total is conserved.
Compensation (subtract)
Shift both numbers up by the same amount to round the subtrahend.
Counting up
Subtraction as bridges. Step from b up to the next round, then to a.
Near-round multiply
Round one factor to the nearest 10 / 100 / 1000, correct with the difference.
Halve and double (decompose)
Move a factor between the two operands to land on a clean number.
Benchmark percentages
Decompose any percentage into a sum of anchor percentages (50, 25, 10, 5, 1).
Estimation
× near anchors
Estimate products by anchoring to a clean nearby number and correcting by the gap.
Sanity check
Read a calculator output. Decide whether it is in the right ballpark or off by 2× / decimal slip / order-of-magnitude.
Divide near anchors
Round the dividend to a clean multiple, divide, correct.
Percent from anchors
Anchor at the nearest 5/10/25/50/75 and correct with the small leftover.
Order of magnitude
Multiply numbers in scientific notation by working mantissa and exponent separately.
Compound scaling
Rate × time, dose × weight, percent chains — round one factor and accept the drift.