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If R={x:x∈N, x²<20}, which set is R?
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Answer and explanation
Correct answer: R={1,2,3,4}
For natural numbers, test successive values in the inequality x²<20. We have 1²=1, 2²=4, 3²=9, and 4²=16, all less than 20. However, 5²=25, which is not less than 20, so no larger natural number can qualify. With N={1,2,3,...}, zero is excluded. Hence R={1,2,3,4}, option A.
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What is the correct answer to this question?
R={1,2,3,4}
Why is this the correct answer?
For natural numbers, test successive values in the inequality x²<20. We have 1²=1, 2²=4, 3²=9, and 4²=16, all less than 20. However, 5²=25, which is not less than 20, so no larger natural number can qualify. With N={1,2,3,...}, zero is excluded. Hence R={1,2,3,4}, option A.
Which subject and chapter does this question cover?
This is a Class 9 Mathematics question. Chapter: Number Systems.
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