Multiply by 25: divide by 4, add two zeros

The trick

$25 = \dfrac{100}{4}$, so multiplying by 25 = dividing by 4 then multiplying by 100.

Snappy examples

• $16 \times 25$ → $16 \div 4 = 4$ → $\times 100$ = 400
• $84 \times 25$ → $84 \div 4 = 21$ → 2100
• $52 \times 25$ → $52 \div 4 = 13$ → 1300

Cousins to know

Trick	Method
$\times 5$	$\div 2$ then $\times 10$
$\times 25$	$\div 4$ then $\times 100$
$\times 50$	$\div 2$ then $\times 100$
$\times 125$	$\div 8$ then $\times 1000$
$\times 250$	$\div 4$ then $\times 1000$

When the division isn’t exact

$27 \times 25$ → $27 \div 4 = 6.75$ → $\times 100$ = 675. Still much faster than long multiplication.

?Your turn

What is 36 × 25?

A.700B.900C.1200D.3600

Check