To identify the irrational numbers from the options given, we need to determine which of these numbers cannot be expressed as a simple fraction (i.e., they are not exact fractions or integers). Here are the evaluations of each option:
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915: This is an integer, so it is a rational number.
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9 over 15: This simplifies to \( \frac{3}{5} \), which is a rational number.
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√9: The square root of 9 equals 3, an integer, so it is rational.
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√169: The square root of 169 equals 13, also an integer, making it rational.
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π (pi): Pi is a well-known irrational number that cannot be expressed as a simple fraction.
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√18: The square root of 18 can be simplified to \( 3\sqrt{2} \), which is irrational because \( \sqrt{2} \) is irrational.
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√78: The square root of 78 is also irrational since it cannot be simplified to a fraction.
From the analysis, the three irrational numbers are:
- π (pi)
- √18
- √78
So, the correct selections for irrational numbers are π, √18, and √78.