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- List the given numbers and units.
- Choose the formula that matches the asked value.
- Simplify carefully and compare with options.
Correct Answer: A
Correct Answer: A
Method / Topic: Probability
The answer follows from the arithmetic relation between the given values.
Short Explanation
Detailed Explanation
Correct Answer: A
Method / Topic: Probability
<table cellspacing="0" style="border-collapse:collapse; height:20px; width:85px">
<tbody>
<tr>
<td style="background-color:#c0e6f5; border-bottom:1px solid #44b3e1; border-left:none; border-right:none; border-top:1px solid #44b3e1; height:20px; vertical-align:top; white-space:normal; width:85px"><span style="color:#000000">Multiples of 4 are 7 numbers and multiples of 5 are 6 numbers. Multiples of both are multiples of 20: only 20, so one overlap. Favourable count=7+6−1=12. Probability=12/30=2/5. The calculation is checked against the conditions in the
. A useful final check is to substitute the
s involving signs, denominators, amount versus interest, and distance versus speed.</span></td>
</tr>
</tbody>
</table>
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Learn + Solve: Shortcut, Trap & Fast Route Click to view shortcut, steps, and common mistake
Shortcut used, common trap, and the fastest solving route
- List the given numbers and units.
- Choose the formula that matches the asked value.
- Simplify carefully and compare with options.
A number is selected at random from 1 to 30. What is the probability that it is divisible by 4 or 5?
Explanation
Correct Answer: A
Method / Topic: Probability
The answer follows from the arithmetic relation between the given values.
Short Explanation
Detailed Explanation
Correct Answer: A
Method / Topic: Probability
<table cellspacing="0" style="border-collapse:collapse; height:20px; width:85px">
<tbody>
<tr>
<td style="background-color:#c0e6f5; border-bottom:1px solid #44b3e1; border-left:none; border-right:none; border-top:1px solid #44b3e1; height:20px; vertical-align:top; white-space:normal; width:85px"><span style="color:#000000">Multiples of 4 are 7 numbers and multiples of 5 are 6 numbers. Multiples of both are multiples of 20: only 20, so one overlap. Favourable count=7+6−1=12. Probability=12/30=2/5. The calculation is checked against the conditions in the
. A useful final check is to substitute the
s involving signs, denominators, amount versus interest, and distance versus speed.</span></td>
</tr>
</tbody>
</table>
See full explanation + shortcut trick
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