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Quantity and Unit Analogy

Introduction

Quantity-Unit analogies test your ability to match a measurable quantity with its standard unit. These questions appear frequently in aptitude tests and measure both basic science literacy and quick recall of common units.

Pattern: Quantity and Unit Analogy

Pattern

The key idea is: the first term is a quantity (what is measured) and the second term is the unit used to measure it. Apply the same quantity → unit mapping to the second pair.

Step-by-Step Example

Question

Time : Seconds :: Weight : ______
(A) Kilogram (B) Pound (C) Gram (D) Meter

Solution

  1. Step 1: Identify the relationship.

    Time → Seconds (quantity → unit).

  2. Step 2: Determine the corresponding unit for the second quantity.

    Weight → Kilogram is the SI base unit for mass/weight measurement.

  3. Step 3: Choose the most standard unit.

    Among options, Kilogram is the standard SI unit (Gram is subunit; Pound is non-SI; Meter is unrelated).

  4. Final Answer:

    Kilogram → Option A

  5. Quick Check:

    Time : Seconds :: Weight : Kilogram ✅

Quick Variations

1. Quantity : SI base unit (e.g., Length : Meter, Time : Second).

2. Quantity : commonly used non-SI unit (e.g., Weight : Pound, Volume : Gallon).

3. Quantity : derived unit (e.g., Force : Newton, Pressure : Pascal).

4. Quantity : metric prefix variation (e.g., Distance : Kilometer vs Meter).

Trick to Always Use

  • Step 1 → Ask: "What is the standard SI/base unit for this quantity?"
  • Step 2 → If SI not an option, choose the most commonly accepted unit in everyday use.
  • Step 3 → Eliminate options that are unrelated dimensions (e.g., length vs mass).

Summary

Summary

  • Identify whether the pair shows quantity → unit or unit → quantity and keep the same direction.
  • Prefer SI/base units (meter, kilogram, second, ampere, kelvin, mole, candela) when available.
  • When SI units are not present, choose the most widely used conventional unit (e.g., pound, liter).
  • Check that the option measures the same physical dimension as the given quantity (mass vs length vs time).

Example to remember:
Time : Seconds :: Weight : Kilogram

Practice

(1/5)
1. Length : Meter :: Temperature : ______
easy
A. Kelvin
B. Pascal
C. Watt
D. Joule

Solution

  1. Step 1: Identify the relationship.

    Length is measured in Meters (quantity → unit).

  2. Step 2: Apply same rule.

    Temperature is measured in Kelvin (the SI base unit).

  3. Final Answer:

    Kelvin → Option A

  4. Quick Check:

    Length : Meter :: Temperature : Kelvin ✅
Hint: Always match the correct SI base unit for the given quantity.
Common Mistakes: Choosing Joule (energy) or Watt (power) due to confusion of units.
2. Force : Newton :: Pressure : ______
easy
A. Joule
B. Pascal
C. Watt
D. Ohm

Solution

  1. Step 1: Observe first pair.

    Force is measured in Newton.

  2. Step 2: Apply same logic.

    Pressure is measured in Pascal (N/m²).

  3. Final Answer:

    Pascal → Option B

  4. Quick Check:

    Force : Newton :: Pressure : Pascal ✅
Hint: Recall derived SI units (Force → Newton, Pressure → Pascal).
Common Mistakes: Selecting Joule (energy) due to familiarity, not correctness.
3. Energy : Joule :: Power : ______
easy
A. Ampere
B. Watt
C. Volt
D. Pascal

Solution

  1. Step 1: Identify first relation.

    Energy is measured in Joules.

  2. Step 2: Apply same quantity-unit rule.

    Power is measured in Watts (1 Watt = 1 Joule/sec).

  3. Final Answer:

    Watt → Option B

  4. Quick Check:

    Energy : Joule :: Power : Watt ✅
Hint: Remember: Power = Energy / Time, unit of Power → Watt.
Common Mistakes: Choosing Volt (potential difference) instead of Watt (power).
4. Electric Current : Ampere :: Resistance : ______
medium
A. Ohm
B. Volt
C. Watt
D. Coulomb

Solution

  1. Step 1: Identify the pattern.

    Electric Current is measured in Amperes.

  2. Step 2: Apply same rule.

    Resistance is measured in Ohms.

  3. Final Answer:

    Ohm → Option A

  4. Quick Check:

    Electric Current : Ampere :: Resistance : Ohm ✅
Hint: Pair electrical quantities with their standard electrical units.
Common Mistakes: Mixing up Volt (potential difference) and Ohm (resistance).
5. Frequency : Hertz :: Work : ______
medium
A. Watt
B. Joule
C. Newton
D. Meter

Solution

  1. Step 1: Observe first relation.

    Frequency is measured in Hertz.

  2. Step 2: Apply same logic.

    Work is measured in Joules.

  3. Final Answer:

    Joule → Option B

  4. Quick Check:

    Frequency : Hertz :: Work : Joule ✅
Hint: Match physical quantities with their standard measurement units.
Common Mistakes: Confusing Work (Joule) with Power (Watt).

Mock Test

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