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3 years ago

The age of a boy is twice that of his sister. five years ago the boy was 3 times the age of his sister. How old is the boy

Mathematics

1 answer:

joja [24]3 years ago

7 0

Answer:

<h2>20 years old.</h2>

Solution,

Let the age of sister be X

Let the age of boy be 2x

Now,

Five years ago,

 $3(x - 5) = 2x - 5 \\ or \: 3x - 15 = 2x - 5 \\ or \: 3x - 2x = - 5 + 15 \\ x = 10$ 

Again,

Replacing value,

 $age \: of \: boy = 2x \\ \: \: \: \: \: \: \: \: \: \: \: \: \: = 2 \times 10 \\ \: \: \: \: \: \: \: \: \: \: \: = 20$ 

hope this helps..

Good luck on your assignment..

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Suppose an airplane climbs 15 feet for every 40 feet it moves forward. What is the slope of this airplane's ascent?

zimovet [89]

$\frac{15}{40}$
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2 years ago

Solve for x: 2/3=8/x+6

Tresset [83]

Answer:

x = 6

Step-by-step explanation:

2/3=8/x+6

Using cross products

2 * (x+6) = 3*8

2(x+6) = 24

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2 years ago

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Express 3080 as a product of prime factors

n200080 [17]

Prime Factors of 3080 =2, 2, 2, 5, 7, 11

Which is the same as = 23 x 5 x 7 x 11

Prime Factors Tree of 3080

3080
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2 years ago

Suppose that x and y are both differentiable functions of t and are related by the given equation. Use implicit differentiation

stepan [7]

Answer:

Let z = f(x, y) where f(x, y) =0 then the implicit function is

$\frac{dy}{dx} =$ $\frac{-δ f/ δ x }{δ f/δ y }$

Example:- $\frac{dy}{dx} = \frac{-(y+2x)}{(x+2y)}$

Step-by-step explanation:

Partial differentiation:-

Let Z = f(x ,y) be a function of two variables x and y. Then

$\lim_{x \to 0} \frac{f(x+dx,y)-f(x,y)}{dx}$ Exists , is said to be partial derivative or Partial differentiational co-efficient of Z or f(x, y)with respective to x.

It is denoted by δ z / δ x or δ f / δ x

Let Z = f(x ,y) be a function of two variables x and y. Then

$\lim_{x \to 0} \frac{f(x,y+dy)-f(x,y)}{dy}$ Exists , is said to be partial derivative or Partial differentiational co-efficient of Z or f(x, y)with respective to y

It is denoted by δ z / δ y or δ f / δ y

Implicit function:-

Let z = f(x, y) where f(x, y) =0 then the implicit function is

$\frac{dy}{dx} =$ $\frac{-δ f/ δ x }{δ f/δ y }$

The total differential co-efficient

d z = δ z/δ x + $\frac{dy}{dx}$ δ z/δ y

Implicit differentiation process

differentiate both sides of the equation with respective to 'x'

move all d y/dx terms to the left side, and all other terms to the right side

factor out d y / dx from the left side
Solve for d y/dx , by dividing

Example : $x^2 + x y +y^2 =1$

solution:-

differentiate both sides of the equation with respective to 'x'

$2x + x \frac{dy}{dx} + y (1) + 2y\frac{dy}{dx} = 0$

move all d y/dx terms to the left side, and all other terms to the right side

$x \frac{dy}{dx} + 2y\frac{dy}{dx} = - (y+2x)$

Taking common d y/dx

$\frac{dy}{dx} (x+2y) = -(y+2x)$

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3 years ago

Explain why the X coordinates of the points where the graphs of the equations y=2^-x and y=4^x+3 intersects

sveta [45]

Hello,

y=2^(-x)
y=2^(2x)+3

==>2^(2x)+3=1/2^x
==>2^(3x)+3*2^x-1=0 (1)
Let's assume u=2^x
(1)==>u^3+3*u-1=0

which as 3 roots
u=0.322185354626 or
u = -0.161092677313 + i1.754380959784 or
u = -0.161092677313 - i1.754380959784.

Let's take the real solution

0.322185354626=2^x
==>x=ln(0.322185354626) / ln(2)
x=-1,6340371790199...

an other way is
f(x)=2^(3x)+3*2^x-1
f(-2)=1/64+3/4-1=-15/64 <0
f(-1)=1/8+1-1=1/8>0
==> there is a solution betheen -2<x<-1

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2 years ago