4. for $a<0.5$

## Correct answer: for $a<1$

## Question 3

Correct

Points: 1.00 out of a maximum of 1.00

Question 4

Correct

Points: 1.00 out of a maximum of 1.00

## Question 5

Correct

Points: 1.00 out of a maximum of 1.00
Worker $A$ and worker $B$ can complete the work in 7.2 days, worker $A$ and worker $C$ in 9 days, worker $B$ and worker $C$ in 12 days. How many days will they take to complete the work if they all work together?
Answer: 6

Correct answer: 6

A piece of copper-tin alloy has a total mass of 12 kg and contains 45% copper. How much pure tin should be added to this piece of alloy to obtain a new alloy containing 40% copper?

Answer: 1.5

Correct answer: 1.5

Find a two-digit number that is three times the product of its digits. If the digits of this number are reversed, the ratio of the resulting number to the given number is $\frac{7}{4}$.

Answer: 24

Correct answer: 24

## Question 7

Correct

Points: 1.00 out of a maximum of 1.00

## Question 8

Correct

Points: 1.00 out of a maximum of 1.00

Question 9

Correct

Points: 1.00 out of a maximum of 1.00
Answer: 8

Correct answer: 8

Three edges emanating from one vertex of a rectangular parallelepiped are equal to $a, b$, c. Find the length of the diagonal of this parallelepiped.

Choose one answer: