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nadya68 [22]
3 years ago
10

John’s father is 5 times older than John and John is twice as old as his sister Alice. In two years time, the sum of their ages

will be 58. How old is John
Mathematics
1 answer:
oksano4ka [1.4K]3 years ago
7 0

Answer:

8 years

Step-by-step explanation:

Let age of father be f

age of John be j

age of Alice be a

John's father is 5 times as old as John. We can write:

f = 5j

John is twice as old as Alice. We can write:

j = 2a

or

a = j/2

SUM OF ALL OF THEIR AGES (after 2 years) will be 58. We can write:

f+2 + j+2 + a+2 = 58

This becomes:

f + j + a + 6 = 58

f + j + a = 52

Now, we replace third equation with the first two (in bold) and get:

f + j + a = 52\\5j + j + \frac{1}{2}j=52\\6.5j=52\\j=8

So John is 8 years old

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We have been given that Jonathan is using the microscope in lab. He saw a chain of bacteria that was 10 millimeters long. We are asked to find the length of chain of bacteria in centimeters.

We know that 1 millimeter is equal to 0.1 centimeter.

To convert 10 milllimeters into centimeters, we will multiply 10 by 0.1.

\text{Length of bacteria in cm}=10\text{ mm}\times \frac{0.1\text{ cm}}{\text{1 mm}}

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3 years ago
The area of a rectangle is 42 ft squared, and the length of the rectangle is 5 ft more than twice the width. Find the dimensions
stira [4]

Answer:

<h3>Length = 12 ft</h3>

Width = \frac{7}{2} ft

Step-by-step explanation:

Given,

Area of rectangle = 42 \:  {ft}^{2}

Width = X

Length = 2x + 5

Now,

x(2x + 5) = 42

2 {x}^{2}  + 5x   = 42

2 {x}^{2}  + 5x - 42 = 0

2 {x}^{2}  + 12x - 7x - 42 = 0

2x(x + 6) - 7(x + 6) = 0

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Either

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Or,

x + 6 = 0

x = 0 - 6

x =  - 6

Negative value can't be taken.

So, width = \frac{7}{2} ft

Again,

Finding the value of length,

Length = 2x + 5

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7 + 5

12

Length = 12 ft

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