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3 years ago

Will is twice as old as Jill. Three years ago, Jill's age was two fifths of Will's age then. How old is each now?

1 answer:

4 0

"Will is twice as old as Jill."

   Jill's age . . . . .   J
   Will's age . . . . 2J .

"Three years ago . . .

   Jill's age then . . . . .   J - 3
   Will's age then . . . . 2J - 3

". . . Jill's age then was 2/5 of Will's age then."

   J - 3 = (2/5) (2J - 3)
Multiply
each side by 5 : 5J - 15 = 2 (2J - 3)

Divide
each side by 2 :    2.5 J - 7.5 = 2J - 3

Subtract 2J
from each side: 0.5 J - 7.5 =    -3

Add 7.5
to each side: 0.5 J = 4.5

Multiply
each side by 2 :    J    = 9

Jill is 9 y.o. now.
Will is 18 y.o. now.

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Answer:

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Step-by-step explanation:

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4 years ago

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The length of a rectangle is 7cm longer than it’s width and the area of the rectangle is 240 m ^2 fond the exact dimensions of t

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Let:

L = Length

W = Width

The length is 7cm longer than its width, so:

$L=W+7$

The area is given by:

$A=W\cdot L$

Therefore:

$\begin{gathered} 240=(W+7)\cdot(W) \\ 240=W^2+7W \\ W^2+7W-240=0 \end{gathered}$

Solve for W using the quadratic formula:

$\begin{gathered} W=\frac{-b\pm\sqrt[]{b^2-4ac}}{2a} \\ W=\frac{-7\pm\sqrt[]{7^2-4(1)(-240)}}{2(1)} \\ W=\frac{-7\pm\sqrt[]{1009}}{2} \\ W\approx12.38238 \\ or \\ W\approx-19.38238 \end{gathered}$

Therefore:

W = 12.38238 since a negative width wouldn't make any sense

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Answer:

W = 12.38238 m

L = 19.38238 m

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