If L={x: x is a positive multiple of 12 less than 120}, what is n(L)?
Answer and explanation
Correct answer: 9
The governing idea is counting positive multiples under a strict upper bound. Write x=12k, where k is a positive integer. The condition 12k<120 gives k<10, so k can be 1,2,...,9. Thus L={12,24,36,48,60,72,84,96,108}, which has 9 elements. The value 120 is excluded because the inequality is strictly less than 120.
Frequently asked questions
What is the correct answer to this question?
9
Why is this the correct answer?
The governing idea is counting positive multiples under a strict upper bound. Write x=12k, where k is a positive integer. The condition 12k<120 gives k<10, so k can be 1,2,...,9. Thus L={12,24,36,48,60,72,84,96,108}, which has 9 elements. The value 120 is excluded because the inequality is strictly less than 120.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Number Systems.
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