For an area of 18m²,the amount of a fertilizer required is 675g. a) how much is needed to fertilise 11m²?
b) what area will 862.5g fertilise?

a) 412.5g

b)23m²

Step-by-step explanation:

a)18m²=675g

11m²=x

by cross multiplication,

18x=11×675

18x=7425

x=7425/18

x=412.5g

b)18m²=675g

y=862.5g

18×862.5=675y

15525=675y

15525/675=y

y=23m²

Step-by-step explanation:

This is a rate problem so using ratios is a good way to calculate the answer for different areas or amounts

     675 g per 18 m²       675/18     g/m²

a)  How many grams for 11m²

     675/18  g/m²   =   ??? / 11 m²            i cross multiply 675 times 11 divide by 18

                                                         or more simply multiply both side by 11

                                                         solving for the ???

            (675)(11) g m² / 18 m²  =  ??? g    =  412.5 grams    ( the m²/m² cancel)

b)  what area can be fertilised with 862.5 g?         again applying ratio

      this time we know the g and want to calculate an unknown area

      675 / 18  = 862.5  / ???        this will take one more step since the ??? is

                                                    in the denominator

      18 / 675  =  ??? / 862.5       I just inverted both sides

      18m² / 675g = ??? / 862.5g      again simply multiply both sides by 862.5g

     (18m²)(862.5g) / (675g) = ???          this time the grams cancel leaving m²

                                 ???   =   23 m²