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

Appeared in: RML Lucknow - 2021

Explanation

The square of 70 is calculated as 70 × 70, which equals 4900.
By counting the trailing zeros in the number 4900, we find there are exactly two zeros.
A general mathematical rule states that if a number ends in 'n' zeros, its square will end in '2n' zeros.
Since the number 70 has one zero (n=1), its square must have 2 × 1 = 2 zeros.

Option A: This is the number of zeros in the original number (70), not in its square.
Option C: A result of three zeros is not obtained by squaring a number ending in a whole number of zeros. For instance, a number with 1.5 zeros is not possible.
Option D: This would be the number of zeros if the original number had two zeros (e.g., 700).

Clinical Relevance

Nursing practice connection: This is primarily an exam-oriented knowledge point with limited direct bedside application, so retain Properties of Squares and Zeros as background academic context rather than a clinical decision trigger.
This question tests general mathematical aptitude and numerical reasoning, which are essential skills for nurses.
Accurate calculation is critical in nursing for tasks like medication dosage calculation, IV drip rate monitoring, and interpreting lab results.
What if the question asked for the square of 700? The number 700 has two zeros (n=2). According to the rule, its square would have 2 × 2 = 4 zeros (700² = 490,000).

How to Approach the Question

First, carefully read the question to understand what is being asked. The question asks for the 'number of zeros' in the 'square of 70'.
Identify the two steps required: first, square the number 70, and second, count the zeros in the result.
Calculate the square of 70: 70 × 70 = 4900.
Count the number of zeros at the end of the result, 4900. There are two zeros.
Alternatively, recall the shortcut: If a number ends with 'n' zeros, its square will end with '2n' zeros. Since 70 has one zero, its square will have 2 × 1 = 2 zeros.
Compare your result with the given options and select the one that matches.

Concept Tested & Keywords

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