Question 945278

1. 

if the length {{{L}}} of a rectangle is {{{3 }}}times the width {{{W}}}, we have

{{{L=3W}}}

 if the perimeter is {{{40}}}=> {{{2(L+W)=40}}} ...substitute {{{L}}} from above

{{{2(3W+W)=40}}}

{{{(4W)=20}}}

{{{W=20/4}}}

{{{W=5}}}

go to {{{L=3W}}}, substitute  {{{5}}} for {{{W}}}

{{{L=3*5}}}

{{{L=15}}}

so, the length is {{{15}}} and the width is {{{5}}}


2. 
the population of a gardens high school is {{{2500}}},
 If the number of males is {{{240}}} more than the number of females, how many males and females are there?

let the number of males be {{{m}}} and  the number of females {{{f}}}

we know that  {{{m+f=2500}}}...eq.1
we also know that {{{m=f+240}}}....eq.2 ...substitute it in eq.1

{{{f+240+f=2500}}}...eq.1...solve for {{{f}}}


{{{2f=2500-240}}}

{{{2f=2260}}}

{{{f=2260/2}}}

{{{highlight(f=1130)}}}->the number of females

now find  {{{m=f+240}}}
{{{m=1130+240}}}

{{{highlight(m=1370)}}}->the number of males