Brain Teasers and Logic Puzzles

Every month in the Gregorian calendar has at least 28 days. While February is the only month with exactly 28 days (in non-leap years), all 12 months contain a 28th day.

You take the first pill immediately, the second after 30 minutes, and the third after another 30 minutes. The total time elapsed is 1 hour (two 30-minute intervals between three pills), not 1.5 hours which would be three intervals.

Dividing 30 by half (0.5) equals 60. Adding 10 gives 70. Many people incorrectly divide 30 by 2 to get 15, then add 10 to get 25. The key is that half means 0.5, not dividing something in half.

This is a lateral thinking puzzle. You must light the match first before you can light any of the items (oil heater, oil lamp, or candle). Since the match isn't listed among the options, NONE of the three items would be lit first.

A standard wind-up mechanical alarm clock does not distinguish between AM and PM. If you set it at 8:00 PM to go off at 9:00, it will ring at 9:00 PM, just one hour later.

The phrase 'all but 9 died' means that 9 sheep survived. Therefore, there are exactly 9 live sheep left. This is a classic lateral thinking riddle designed to make you subtract 9 from 17 incorrectly.

Working backwards: Three days after Saturday is Tuesday. The day before the day before yesterday equals 3 days ago. If 3 days ago was Tuesday, then today is Friday (Tuesday + 3 days = Friday).

To solve this problem, the user needs to know basic arithmetic and how to find the sum of two numbers. The user must check whether any two numbers in the given list add up to thirteen.

Let's go through each option:

A. True: This option is correct. By checking the given numbers, we can see that 2 of them add up to 13. 6 and 7 add up to 13. Thus, option A is the correct answer.

B. False: This option is incorrect. There are actually two numbers in the given list that add up to 13.

Therefore, the answer is:

The Answer is: A

To find the fraction with the lowest denominator, compare the bottom numbers: 6, 7, 9, 4, and 3. The smallest is 3, so 7/3 (Option E) has the lowest denominator. This is a straightforward comparison task.

The notation "10¼" means "10 to the power of 4" (10^4), which is 10 × 10 × 10 × 10 = 10000. Option B is correct. This is exponent notation where ¼ represents the power 4.

First convert 2m to 200cm. Set up the proportion: 80cm costs 16p, so 1cm costs 16/80 = 0.2p. Therefore 200cm costs 200 × 0.2 = 40p. Option C is correct.

Simplify the left side: 3x + x = 4x. So 4x = 2x + 2y. Subtract 2x from both sides: 2x = 2y. Divide by 2: x = y. Option D is correct.

Count the 9s in two places: the units position (9, 19, 29, ..., 99) gives 10 occurrences. The tens position (90, 91, 92, ..., 99) gives 10 more. But 99 has two 9s, so total = 10 + 10 = 20. Option D is correct.

Convert 1/5 to 3/15 (multiply numerator and denominator by 3). Then add: 3/15 + 7/15 = 10/15. Simplify by dividing numerator and denominator by 5: 10/15 = 2/3. Option D is correct (2/3 = 0.666...).

Calculate 10% of £900: 900 × 0.10 = £90. Subtract this discount from the original price: £900 - £90 = £810. Option B is correct.