Question

If x varies directly as 3y and x=7 when y=5,find y when x=14​

Answer 1

Answer:

y = 21

Step-by-step explanation:

x α y ___ (given)

x = k 3y ___ (k is constant of variation)

when x = 7 & y =5

$\implies \sf{\dfrac{7}{5} }$

   

• 7 and 5 are not divisible with any table. Hence, k = 7/5

   

$\therefore \; \underline{\boxed{\pmb{\sf{\dfrac{7}{5} = k}}}}$

   

Constant of variation (k) = 7/5

y = 7/5(3y) is the equation of variation

   

Solving the equation y = 7/5(3y) ;;

[tex]\implies \sf{y = \dfrac{7}{5} \times 3y}\\ \\ \implies \sf{y = \dfrac{7}{5} \times 3 \times 5 ... ... \big\langle given \; that \; \red{ y = 5} \big\rangle } \\ \\ \implies \sf{ y = \dfrac{7}{\cancel{5}} \times \cancel{15}}\\ \\ \implies \sf{y = 7 \times 3}\\ \\ \implies \underline{\boxed{\pmb{\sf{y = 21}}}}[/tex]

   

Therefore, the value of y is 21! :D

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