18 is 45% of what ?

↳Redirected from "Suppose that I don't have a formula for #g(x)# but I know that #g(1) = 3# and #g'(x) = sqrt(x^2+15)# for all x. How do I use a linear approximation to estimate #g(0.9)# and #g(1.1)#?"
3 Answers
Lucia C. · Stefan V.
Apr 20, 2018

#40#

Explanation:

#18/40# will give you #0.45#, which is equal to #45%#.

How to solve it:

  1. #" "18 = 0.45x#

  2. #" "18/0.45 = x#

  3. #" "40 = x#

Karan N. · Stefan V.
Apr 20, 2018

#40#

Explanation:

The proportion I like to use with these types of problems goes like:

#"percent"/100 = "part"/"whole"#

Part/whole can also be written as "is/of"

So in this case:

  • The part (is) is #18#
  • The whole (of) is unknown to us - let's say #x#
  • The percent (%) is #45#

Now:

#45/100 = 18/x#

We can cross multiply to get:

#45x = 1800#

#x = 40#

Hope this helps!

Meave60
Apr 20, 2018

#18# is #45%# of #40#.

Explanation:

Let #x# represent the unknown number.

#45%=45/100=0.45#

#0.45x=18#

Divide both sides by #0.45#.

#x=18/(0.45)#

#x=40#

Check.

#0.45(40)=18#

#18# is #45%# of #40#.

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