We have four problems to solve: Problem 27: Subtract two fractions: $\frac{3}{10} - \frac{1}{20}$. Problem 28: Divide 725 by 29. Problem 29: Calculate 15% of 440. Problem 30: Multiply 6574 by 31.

1. Problem Description

We have four problems to solve:

Problem 27: Subtract two fractions: $\frac{3}{10} - \frac{1}{20}$.

Problem 28: Divide 725 by

2

9. Problem 29: Calculate 15% of

4

4

0. Problem 30: Multiply 6574 by

3

1.

2. Solution Steps

Problem 27:

To subtract the fractions, we need a common denominator. The least common multiple of 10 and 20 is

2

0. So, we rewrite the first fraction with a denominator of

2

0. $\frac{3}{10} = \frac{3 \times 2}{10 \times 2} = \frac{6}{20}$

Now we can subtract:

$\frac{6}{20} - \frac{1}{20} = \frac{6-1}{20} = \frac{5}{20}$

Finally, simplify the fraction:

$\frac{5}{20} = \frac{1}{4}$

Problem 28:

We need to divide 725 by

2

9. $725 \div 29$

29 goes into 72 twice. $2 \times 29 = 58$.

$72 - 58 = 14$

Bring down the

5. Now we have

1

4

5. 29 goes into 145 five times. $5 \times 29 = 145$

$145 - 145 = 0$

So, $725 \div 29 = 25$.

Problem 29:

To calculate 15% of 440, we can multiply 440 by 0.15 or find 10% and 5% separately and add them.

$15\% \times 440 = 0.15 \times 440$

$0.15 \times 440 = 66$

Alternatively:

$10\% \times 440 = 44$

$5\% \times 440 = \frac{1}{2} \times 10\% \times 440 = \frac{1}{2} \times 44 = 22$

$15\% \times 440 = 10\% \times 440 + 5\% \times 440 = 44 + 22 = 66$

Problem 30:

We need to multiply 6574 by

3

1. $6574 \times 31$

First, multiply by 1:

$6574 \times 1 = 6574$

Next, multiply by 30:

$6574 \times 30 = 6574 \times 3 \times 10 = 19722 \times 10 = 197220$

Now, add the two results:

$6574 + 197220 = 203794$

3. Final Answer

Problem 27: $\frac{1}{4}$

Problem 28: 25

Problem 29: 66

Problem 30: 203794