Long multiplication for the 11 plus

Split 24 into 20 and 4. Do 36 times 4. Then do 36 times 20, which is 36 times 2 with a zero on the end. Add the two answers. The grid method shows the same thing as a table: break both numbers into tens and units and fill the boxes.

36 times 4 is 144. Now the second row. We are multiplying by twenty, so first put a zero in the units. Then 36 times 2 is 72. That makes 720. 144 plus 720 is 864.

The trap is leaving out the zero. Then the second row is 72, not 720, and the total comes to 216, which is far too small. 36 times 24 is about 30 times 20, so about 600. Estimating catches it every time.

Part of the Arithmetic topics for the 11+.

• 2.1Mental addition and subtractionRound to a friendly number, then adjust
• 2.2Column additionCarry the ten, every time
• 2.3Column subtractionHow to borrow from a zero
• 2.4Multiplication tablesBuild the facts you cannot remember
• 2.5Short multiplicationMultiply first, then add the carry
• 2.7DivisionEvery digit needs an answer above it
• 2.8Order of operationsOne sum, one agreed order

Every 11 plus maths topic