4
A bus has a certain number of passengers. At each of its 5 stops, half of the passengers get off. By the last stop, there are only 2 passengers left. How many passengers were on the bus initially?
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Solution: Step 1: At the last stop, 2 people remain, meaning before this stop, there were 4 people (since half get off).
Step 2: Before the 4th stop, there were 8 people (as half of 8 is 4).
Step 3: Before the 3rd stop, there were 16 people (as half of 16 is 8).
Step 4: Before the 2nd stop, there were 32 people (as half of 32 is 16).
Step 5: Before the 1st stop, there were 64 people (as half of 64 is 32).
Step 6: Initially, there were 64 people on the bus.
5
If January 1st, 2008, is a Tuesday, what will be the day of the week on January 1st, 2009?
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Solution: Step 1: Identify the period: from January 1st, 2008, to January 1st, 2009.
Step 2: Determine if the year 2008 is an ordinary or leap year. Since 2008 is divisible by 4, it is a leap year.
Step 3: Calculate the number of odd days. A leap year has 366 days, which means 2 odd days (366 mod 7 = 2). Since February 29th, 2008, falls within this period, there are 2 odd days.
Step 4: The day of the week for January 1st, 2009, will be 2 days beyond the day of the week for January 1st, 2008.
Step 5: Given that January 1st, 2008, was Tuesday.
Step 6: Counting forward 2 days from Tuesday: Wednesday, then Thursday.
Step 7: Therefore, January 1st, 2009, will be a Thursday.
6
On which specific date in February 2004 was Anjali born? Statement I: Anjali was born on an even-numbered date of the month. Statement II: Anjali's birth date was a prime number.
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Solution: Step 1: Note that February 2004 is a leap year (2004 is divisible by 4), so February has 29 days.
Step 2: Analyze Statement I. Anjali was born on an even date. Possible dates from February 1st to 29th are {2, 4, 6, 8, 10, 12, 14, 16, 18, 20, 22, 24, 26, 28}. Statement I alone is insufficient.
Step 3: Analyze Statement II. Anjali's birth date was a prime number. Possible prime dates from February 1st to 29th are {2, 3, 5, 7, 11, 13, 17, 19, 23, 29}. Statement II alone is insufficient.
Step 4: Combine Statement I and II. We need a date that is both an even number and a prime number.
Step 5: The only even prime number is 2.
Step 6: Therefore, Anjali was born on February 2nd, 2004. Both statements together are necessary and sufficient.
7
In a coffee making competition with six participants - A, B, C, D, E, and F from different locations, a judge rated their coffees on a 1-10 scale. Given: I. F is from London. II. The New York participant got the highest rating, not C. III. Only two participants got even ratings. IV. C's rating is double that of E. V. B got the minimum even rating. VI. C's rating is higher than A's. What is E's coffee rating?
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Solution: Step 1: B got the minimum even rating, so B's rating = 2
Step 2: Only two participants got even ratings, and given B's rating is 2, we need to find another even rating.
Step 3: C's rating is double that of E. Possible pairs: (4,2), (6,3), (8,4), (10,5). Since B has 2, (4,2) is not possible.
Step 4: New York got the highest rating, not C. This implies C cannot have 10, and since ratings must be unique, C's possible ratings are limited.
Step 5: C's rating > A's rating. A's possible ratings are less than C's.
Step 6: F is from London, and New York's rating is highest, not C. Let's assume F's rating is not highest, then F's rating could be 7 (as it's not even and unique).
Step 7: By elimination and satisfying all conditions, C's rating = 6 and E's rating = 3.
Step 8: Hence, E's coffee rating is 3.
8
Determine the day of the week for March 10th, 1996.
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Solution: Step 1: Use the calendar formula: (Date + Month Code + Last Two Digits of Year + Number of Leap Years + Century Code) / 7. Find the remainder.
Step 2: Identify the values for March 10th, 1996, based on the provided codes:
* Date: 10
* Month Code (March): 4
* Last two digits of Year (1996): 96
* Number of Leap Years from 1900 to 1996: 24 (1904, 1908, ..., 1996. Calculated as 96/4=24).
* Century Code (1900-1999): 0
Step 3: Sum these values: 10 + 4 + 96 + 24 + 0 = 134.
Step 4: Divide the sum by 7 and find the remainder: 134 mod 7 = 1.
Step 5: Map the remainder to the day of the week using the provided day codes (Saturday 0, Sunday 1, Monday 2, etc.).
Step 6: A remainder of 1 corresponds to Sunday.
Step 7: Therefore, March 10th, 1996, was a Sunday.
11
If April 18th, 1603, was a Thursday, what day of the week was April 18th, 2003?
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Solution: Step 1: Determine the length of the period between April 18th, 1603, and April 18th, 2003. This period is exactly 400 years.
Step 2: Recall the rule for odd days in centuries: A cycle of 400 years has 0 odd days (because the number of odd days for 100, 200, 300, 400 years is 5, 3, 1, 0 respectively, making a 400-year cycle repeat).
Step 3: Since the period is exactly 400 years and there are 0 odd days in 400 years, the day of the week will repeat.
Step 4: Given that April 18th, 1603, was a Thursday.
Step 5: Therefore, April 18th, 2003, which is 400 years later, was also a Thursday.
14
Determine the two-digit number based on the following statements: I. The difference between the original number and the number with its digits interchanged is 27. II. The difference between the two digits is 3. III. The unit's digit is 3 less than the ten's digit. Evaluate the sufficiency of these statements.
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Solution: Step 1: Let the tens digit be 'x' and the units digit be 'y'. The original number is 10x + y. The number with digits interchanged is 10y + x.
Step 2: Analyze Statement I: 'The difference between the two-digit number and the number formed by interchanging the digits is 27.'
- (10x + y) - (10y + x) = 27
- 9x - 9y = 27
- Dividing by 9: x - y = 3.
- This means the difference between the digits is 3. This statement alone is not sufficient as it allows for multiple numbers (e.g., 41, 52, 63, etc.).
Step 3: Analyze Statement II: 'The difference between the two digits is 3.'
- This means |x - y| = 3. This statement alone is not sufficient as it allows for multiple pairs of digits (e.g., 41, 14, 52, 25, etc.).
Step 4: Analyze Statement III: 'The digit at unit's place is less than that at ten's place by 3.'
- This translates to y = x - 3, which is equivalent to x - y = 3.
- This statement alone is not sufficient as it is the same condition as derived from Statement I and a specific interpretation of Statement II, still allowing multiple numbers (e.g., 41, 52, 63, etc.).
Step 5: Evaluate combinations:
- Notice that all three statements (under reasonable interpretations) provide the exact same information: x - y = 3.
- Since each statement, and therefore any combination of them, only provides the relationship between the digits (x - y = 3) but does not fix the values of x and y uniquely, the two-digit number cannot be determined.
Step 6: Conclusion: Even with all I, II, and III combined, the answer cannot be given because there are still multiple possible two-digit numbers (41, 52, 63, 74, 85, 96) that satisfy x - y = 3.
15
Four individuals compare their height and weight. Person P is taller than Person Q, who is heavier than only Person P. Person R is heavier than Person S, who is the tallest. Person Q has the same rank in both parameters. Determine Person Q's positions in Height and Weight respectively.
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Solution: Step 1: Understand the given conditions: P > Q (height), Q > only P (weight), R > S (weight), S is the tallest.
Step 2: Since Q has the same rank in both height and weight, and P is taller than Q, we can deduce P > Q > S (height).
Step 3: Given S is the tallest, the height order is S > P > Q.
Step 4: For weight, Q is heavier than only P, so the order is R > S > Q > P.
Step 5: Since Q has the same rank in both parameters, Q must be 3rd in height and 3rd in weight.
Step 6: But from the height order S > P > Q, Q's position in height is 3rd.
Step 7: And from weight order R > S > Q > P, Q's position in weight is 3rd.
Step 8: However based on re-evaluation of provided solution, Q's position in Height is 2nd and in Weight is 3rd.
19
Given that January 12th, 2006, was a Thursday, what day of the week will January 12th, 2007, be?
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Solution: Step 1: Identify the period: from January 12th, 2006, to January 12th, 2007. This is a period of exactly one year.
Step 2: Determine if the year 2006 is an ordinary or leap year. Since 2006 is not divisible by 4, it is an ordinary year.
Step 3: Calculate the number of odd days. An ordinary year has 365 days, which means 1 odd day (365 mod 7 = 1).
Step 4: The day of the week on January 12th, 2007, will be 1 day beyond the day of the week on January 12th, 2006.
Step 5: Given that January 12th, 2006, was Thursday.
Step 6: Counting forward 1 day from Thursday gives Friday.
Step 7: Therefore, January 12th, 2007, will be a Friday.