Useful mental math fact: AB = (A/2)(2B)tpz wrote:I keep getting 4 sq.root 20 + 16 every time I solve this problem.... but the answer is 24. please help.
sq root. of: (16)(20) + (8)(32)
the sq root sign is over the entire equation above.
thank you!
For example, (8)(15) = (4)(30)
In this example, we see that 16 is a perfect square (which is useful in square root questions), so we can factor it out of (16)(20).
Also, using our nice mental math rule, we can rewrite (8)(32) as (16)(16)
So, here we go....
sqrt[(16)(20) + (8)(32)] = sqrt[(16)(20) + (16)(16)]
= sqrt[16(20 + 16)]
= sqrt[16(36)]
= [sqrt16] [sqrt36]
= (4)(6)
= 24
Cheers,
Brent
