Multiplication looks at equally sized groups. Can you solve this problem?
$3\times9$3×9
Let's look at how to multiply numbers by $6$6.
$6$6 groups is twice (two times) as many as $3$3 groups. Doubling means multiplying equally sized groups by $2$2.
$6\times3$6×3
You can use a doubling strategy to multiply a number by $6$6. Start by multiplying the number by $3$3, then double the answer.