###### Asked in Math and Arithmetic

Math and Arithmetic

# Simple number series If 16 1 88 4 109 2 then 10?

## Answer

###### Wiki User

###### June 13, 2015 9:41PM

5

## Related Questions

###### Asked in Math and Arithmetic

### What number that add to make 20 and times to make -9?

I think you probably want it the other way around: numbers that
add to -9 and multiply to 20. These would be -4 and -5.
How you wrote it:
x + y = 20
xy = -9
x = 20 - y
(20 - y)y = -9
-y^2 + 20y = -9
y^2 - 20y - 9 = 0
(-(-20) +/- sqrt((-20)^2 - 4(1)(-9)))/(2(1)) = y
(20 +/- sqrt(436))/2
10 +/- 2sqrt(109)/2
10 +/- sqrt(109) = y
x + y = 20
x + (10 +/- sqrt(109) = 20
If +,
x + 10 + sqrt(109) = 20
x = 10 - sqrt(109)
If -,
x + 10 - sqrt(109) = 20
x = 10 + sqrt(109)
The two numbers are thus:
10 + sqrt(109) and 10 - sqrt(109)
Check:
x + y = 20
(10 + sqrt(109)) + (10 - sqrt(109)) = 20
10 + 10 + sqrt(109) - sqrt(109) = 20
20 = 20
xy = -9
(10 + sqrt(109))(10 - sqrt(109)) = -9
Difference of squares => (a+b)(a-b)=(a^2 - b^2)
10^2 - sqrt(109)^2 = -9
100 - 109 = -9
-9 = -9
The solutions do work, so the numbers are:
10 + sqrt(109) and 10 - sqrt(109)

###### Asked in Math and Arithmetic

### What is 18 percent off 109?

Here is an easy way to always calculate percentages. Always base
your percentages off 1%, 5%, and 10%.
In our case we have 18%, which can be composed of 10%, 5%, and 3
- 1%'s.
You can always find 10% of any number by moving the decimal
point one place to the left. 5% can be found by simply cutting 10%
in half. 1% can be found by moving the decimal point two places to
the left.
10% of 109 is 10.9
5% of 109 is 10.9 Ã· 2 = 5.45
1% of 109 is 1.09
So now we throw together our simple math problem.
10.9 (10%) + 5.45 (5%) + (1.09 x 3) (3%)
10.9 + 5.45 = 16.35
16.35 + (1.09 x 3) = 3.27
16.35 + 3.27 = 19.62
Lastly we subtract.
109 - 19.62 = 89.38.

Load More