Question

Subtract 8-4 1/2. A. 3 B. 4 C. 4 1/2 D. 3 1/2

Answer 1

Think about it logically. The answer is 4 1/2, since 4 was subtracted from 8, and there is still the 1/2. 

Answer 2

1.
An expression of the form $a \frac{b}{c}$ is called a "compound fraction"
 
Compound fractions can be written as simple fractions by multiplying c to a, and then adding the product to c as follows:

$a \frac{b}{c}= \frac{c.a+b}{c}$

for example, 

$4\frac{1}{2}$ can be written as: 

$4\frac{1}{2}= \frac{2.4+1}{2}=\frac{9}{2}$

2.

when we subtract or add a fraction $\frac{m}{n}$ from an integer k, 

we first write k as a fraction with denominator n. We can do this as follows:

$k=k. \frac{n}{n}= \frac{kn}{n}$

for example, if we want to subtract $\frac{9}{2}$ from 8, 

we first write 8 as a fraction with denominator 2:

$8=8. \frac{2}{2}= \frac{8.2}{2}= \frac{16}{2}$

3.

Thus, 

$8-4 \frac{1}{2}= \frac{16}{2}- \frac{9}{2}= \frac{16-9}{2}= \frac{7}{2}$

4.

The simple fraction 7/2 is not an option, so we write it as a compound fraction as follows:

$\frac{7}{2}= \frac{6+1}{2}= \frac{6}{2}+ \frac{1}{2}=3+ \frac{1}{2}=3\frac{1}{2}$

(So write 7 as the sum of the largest multiple of 2, smaller than 7 + what is left. In our case these numbers are 6 and 1, then proceed as shown)

5. Answer: D