# Math Help - series

1. ## series

4 , 16 , 8 , 40 , 20 , 120 , 60 , 420 , _______

can anybody know on the next number of the blank? because i dont get the pattern ... please help.

thanks guys.

2. ## Re: series

the pattern:
multiply by 4
divide by 2
multiply by 5
divide by 2
multiply by 6
divide by 2
multiply by 7
divide by 2
so next you need to multiply by 8 to get 3360.

3. ## Re: series

Hello, rcs!

$\text{Find the next number: }\:4,16,8,40,20,120,60,420,\_\_$

Examine what happens between numbers . . .

. . $\begin{array}{cccccccccccccccccc} 4 && 16 && 8 && 40 && 20 && 120 && 60 && 420 && ? \\ & \times4 && \div2 && \times5 && \div2 && \times 6 && \div2 && \times7 && ? \end{array}$

Got it?

4. ## Re: series

thanks soroban.. you are the best!