What will be the number of zeros in the square of 70?

Appeared in: RML 2023

Explanation

The square of 70 is calculated by multiplying the number by itself: 70 × 70 = 4900.
The resulting number, 4900, has exactly two zeros at the end.
A general mathematical rule states that if a number has 'n' trailing zeros, its square will have '2n' trailing zeros.
Since 70 has one trailing zero (n=1), its square must have 2 × 1 = 2 trailing zeros.

Option A: This is the number of zeros in the original number (70), not in its square.
Option C: There is no mathematical operation related to squaring 70 that results in three zeros. This is an arbitrary incorrect value.
Option D: This would be the number of zeros if the original number had two zeros (e.g., 700). The square of 700 is 490,000, which has four zeros.

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Properties of squares and number of trailing zeros as background academic context rather than a clinical decision trigger.
This question tests basic mathematical aptitude and number theory, which is a common component of the non-nursing, general intelligence section of nursing recruitment exams.
Proficiency in quick mental calculations and understanding numerical properties is a valuable skill for problem-solving in timed exam environments.
What if? - If the question asked for the number of zeros in the cube of 70? The rule is that the number of zeros would be 3n. Since 70 has one zero, its cube (70 × 70 × 70 = 343,000) would have 3 × 1 = 3 zeros.

How to Approach the Question

Step 1: Identify the core task from the question, which is to find the 'number of zeros' in the 'square of 70'.
Step 2: Recall the definition of a square: a number multiplied by itself.
Step 3: Perform the calculation: 70 × 70.
Step 4: To simplify, multiply the non-zero parts (7 × 7 = 49) and then append the total number of zeros from the original numbers (one from the first 70 and one from the second 70, making two zeros). The result is 4900.
Step 5: Count the number of zeros in the final product, 4900. There are two zeros.
Step 6: Match your result (2) with the given options to find the correct answer.

Concept Tested & Keywords

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Practise the full RML 2023

Attempt every question from this paper in a timed mock, then review the full solution for each one.