4x-3y=2 3x=5y=16 solve using substitution method

1 answer:

7 0

$\left\{\begin{array}{ccc}4x-3y=2&|\text{add 3y to both sides}\\3x+5y=16\end{array}\right\\\left\{\begin{array}{ccc}4x=3y+2&|\text{divide both sides by 4}\\3x+5y=16\end{array}\right\\\left\{\begin{array}{ccc}x=0.75y+0.5&(*)\\3x+5y=16\end{array}\right\\\\\text{substitute}\ (*)\ \text{to the second equation}\\\\3(0.75y+0.5)+5y=16\qquad\text{use distributive property}\\\\(3)(0.75x)+(3)(0.5)+5y=16\\\\2.25y+1.5+5y=16\qquad\text{subtract 1.5 from both sides}\\\\7.25y=14.5\qquad\text{divide both sides by 7.25}$

$\boxed{y=2}\\\\\text{substitute the value of y to}\ (*):\\\\x=0.75(2)+0.5\\\\x=1.5+0.5\\\\\boxed{x=2}\\\\Answer:\ x=2\ and\ y=2\to(2,\ 2)$

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Answer:

84.5 m

Step-by-step explanation:

It is often helpful to draw a diagram for word problems involving geometric relationships. One for this problem is shown below.

The mnemonic SOH CAH TOA reminds you of the relationship between sides of a right triangle:

Tan = Opposite/Adjacent

Here we're given angles of depression measured from the horizontal (as shown in the diagram), but it is more convenient to use angles measured from the vertical. In particular, ∠BAO is the complement of 60°, and its tangent is the ratio OB/OA:

tan(30°) = OB/OA

OB = (200 m)·tan(30°) ≈ 115.47 m . . . . . . multiply by OA, use OA=200 m

Likewise, we have ...

OC = (200 m)·tan(45°) = 200 m

Then the width of the river is the difference between these values:

BC = OC -OB = 200 m - 115.47 m = 84.53 m