$\frac{5.4 \div 3 \times 16 \div 2}{18 \div 5 \times 6 \div 3}$
Aptitude
Surds and Indices
Difficulty: Medium
Choose an option
-
A$2$
-
B$4$
-
C$6$
-
D$8$
Answer
Correct Answer: $2$
Explanation
### Concept & Strategy
This question evaluates your strict adherence to the BODMAS / PEMDAS rule (Order of Operations). For sequences containing only multiplication and division, you must evaluate the expression strictly from left to right.
$$\text{Evaluate } \div \text{ and } \times \text{ strictly from Left to Right}$$
### Step-by-Step Solution
* **Given:**
Numerator: $5.4 \div 3 \times 16 \div 2$
Denominator: $18 \div 5 \times 6 \div 3$
* **Calculation / Deduction:**
1. Evaluate the numerator strictly left to right:
* Step 1: $5.4 \div 3 = 1.8$
* Step 2: $1.8 \times 16 = 28.8$
* Step 3: $28.8 \div 2 = 14.4$
* Numerator result = $14.4$
2. Evaluate the denominator strictly left to right:
* Step 1: $18 \div 5 = 3.6$
* Step 2: $3.6 \times 6 = 21.6$
* Step 3: $21.6 \div 3 = 7.2$
* Denominator result = $7.2$
3. Divide the simplified numerator by the simplified denominator:
$$\frac{14.4}{7.2} = 2$$
### Exam Strategy & Shortcut
**Fractional Conversion:** Instead of dealing with decimals, convert division signs into multiplication by reciprocals. This allows you to cancel terms efficiently.
Numerator: $5.4 \times \frac{1}{3} \times 16 \times \frac{1}{2} = 5.4 \times \frac{16}{6} = 5.4 \times \frac{8}{3} = 1.8 \times 8 = 14.4$
Denominator: $18 \times \frac{1}{5} \times 6 \times \frac{1}{3} = \frac{18 \times 6}{15} = \frac{108}{15} = 7.2$
Result: $\frac{14.4}{7.2} = 2$.
### Common Pitfall
The most common mistake is performing multiplication before division regardless of their order. For example, in the denominator $18 \div 5 \times 6 \div 3$, a student might wrongly calculate $5 \times 6 = 30$ first, completely ruining the evaluation sequence and resulting in an incorrect fraction.
### Final Answer
**Therefore, the correct answer is $2$.**