If A=450 , h=9 find the value of b ?

Question

in the formula A=1/2bh , If A=450 , h=9 find the value of b ?

Answer 1

Think for a few seconds about the "best practice" process.  You may either (1) substitute known values of variables then solve for the one unknown value, or you may (2) solve the original equation for the one unknown in terms of the other variables and then substitute the known values.

 

For example, π is defined as C/d, but we often start with C=πd or C=2πr rather than immediately substituting for C or D.

 

For this problem,

     A = (1/2)bh

 so,

      b = 2A/h

and,

      b = 2(450)/9

      b = 100

 

Note: With this starting formula, I can easily say "twice 450 is 900, divided by 9 is 100."   (converting to decimals is unnecessary, various algebra steps have already been accomplished).  I can also perform a very quick check:  a rectangle with h=9 and b=100 has area of 900; a triangle with those dimensions has half of the area.

 

Answer 2

Hi Alex,

 

 

    in the formula A=1/2bh , If A=450 , h=9 find the value of b ?

 

 

For this question, substitute the given values in for the variables in the formula.

 

 

Given formula:                           A=.5bh

Substitute values:                  450=.5b(9)

Combine like terms:                450=4.5b

divide both sides by 4.5:          100=b

 

 

ANSWER:  b=100

        

Hope this helps you understand the process.

 

Answer 3

Hi Alex,

 

This is just a matter of rearranging the furniture. . .

 

450 = (1/2)b(9)

 

So first divide both sides by 9 to get rid of the 9 on the right side--> 50 = b/2  (remember that one half times b is the same as half of b which is the same as b divided by 2 which is the same as b/2)

 

Now multiply both sides by 2 to get rid of the 2 on the right side--> 100 = b

 

Dan