Rectangular 5611

The rectangular course is 12 m longer than its width. Suppose its length increases by 10 m and its area increases by 600 square meters. What are its dimensions?

Correct answer:

a =  72 m
b =  60 m

Step-by-step explanation:

$$\begin{gathered} a=12+b \\ S=ab \\ ab+600=(a+10)\cdot b \\ a(a-12)+600=(a+10)\cdot (a-12)=(72+10)\cdot (72-12)=-120 \\ 10a=720 \\ a=720/10=72\text{m} \end{gathered}$$

$$\begin{gathered} b=a-12=72-12=60=60\text{m} \\ S=a\cdot b=72\cdot 60=4320{\text{m}}^2 \end{gathered}$$

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