J has read 160 pages in a book. This is 4/5 of the entire book. How many pages does the book have?

Answer 1

Let x be the number of pages in the book.
We know that 4/5 of the book's entire length is 160 pages, so 4/5 * x = 160.
Multiplying both sides of the equation by 5/4, we get x = 200 pages.
Therefore, the book has 200 pages. Answer: \boxed{200}.

Answer 2

S is twice as old as B. In 5 years, the sum of their ages will be 25 years. Find their present ages.

Answer 3

Let's assume B's present age is x.
Therefore, S's present age is 2x, as S is twice as old as B.
In 5 years, B's age will be x + 5, and S's age will be 2x + 5.
According to the problem, the sum of their ages in 5 years will be 25 years.
So, we have the equation x + 5 + 2x + 5 = 25.
Combining like terms, we get 3x + 10 = 25.
Subtracting 10 from both sides of the equation, we get 3x = 15.
Dividing both sides of the equation by 3, we get x = 5.
So, B's present age is x = 5 years.
And S's present age is 2x = 2 * 5 = 10 years.
Therefore, B is 5 years old and S is 10 years old. Answer: \boxed{5, 10}.

Answer 4

A rectangle is 15 cm wide. Find the area and perimeter of the rectangle if it’s width is 3/5 of its length.

Answer 5

Let's assume the length of the rectangle is x cm.
Given that the width is 3/5 of the length, we have the equation:
Width = 3/5 * Length
15cm = 3/5 * x
Multiplying both sides of the equation by 5/3, we get:
x = 15cm * 5/3
x = 25cm
So, the length of the rectangle is 25 cm.
The area of a rectangle is given by the formula A = length * width.
Therefore, the area of the rectangle is:
A = 25cm * 15cm
A = 375 cm^2

The perimeter of a rectangle is given by the formula P = 2 * (length + width).
Therefore, the perimeter of the rectangle is:
P = 2 * (25 cm + 15 cm)
P = 2 * 40 cm
P = 80 cm

Therefore, the area of the rectangle is 375 cm^2 and the perimeter is 80 cm. Answer: \boxed{375 \, \text{cm}^2, 80 \, \text{cm}}.