Numbers and Counting
What is the smallest integer (whole number) that you can write using only two digits?
10
A father leaves home 5 minutes before his son. If the son walks faster, how do you calculate exactly when he catches up?
Divide the father's head-start distance by the difference in their speeds
I drove from the city to the gardens. It took 1 hour and 30 minutes. Driving back the same way took 90 minutes. Why?
1 hour and 30 minutes is the exact same as 90 minutes!
Which would you say is heavier: a pound of light cotton or a pound of heavy, solid gold?
They both weigh exactly one pound!
A small 8-tooth cog-wheel is linked to a large 24-tooth cog-wheel. How many times must the small wheel spin on its own axis to travel once around the big one?
4 times
Can you write the number 31 using only the digit 3 exactly five times?
33+ 3 + (3/3)
A grandfather, two fathers, and two sons went fishing. They caught 3 fish, and everyone got one. How?
There were only 3 people: a grandfather, his son, and his grandson.
Supposing a wall clock takes 7 seconds to strike 7 o'clock, how long will it take the same clock to strike 10 o'clock?
10.5 seconds (there are 6 intervals in 7 strikes, so 1.16 seconds per interval), or 3hrs and 7 secs
A shopkeeper mistakenly switches a $10 note and a $5 note while giving change. Who loses money, and how much?
The shopkeeper loses $5.
Two trains start at the equator heading in opposite directions at the same speed on different tracks. Which train wears out its wheels first?
The train running counter to the Earth's rotation due to friction.
What is the biggest number that you can write using four 1s?
1111
Next door live 4 brothers. Their average height is 74 inches. The first three differ by 2 inches each. The last differs by 6 inches. How tall are they?
70, 72, 74, and 80 inches.
50 minutes ago, it was 4 times as many minutes past 3 o'clock as it is now until 6 o'clock. What time is it now?
5:34
You have 1,000 peanuts shared among friends. If each person gets an equal share and 5 are left over, how many friends are there?
995 is divisible by 5, 9, or 199 friends.
A man walks up a moving escalator in 30 seconds. If he stands still, it takes the escalator 60 seconds to move him up. How long if he walks while it is turned off?
60 seconds
Can you find a peculiar number that is exactly three times the sum of its own digits?
27.. because (2 + 7 = 9) and ( 9 * 3 = 27)
In a family, each boy has as many sisters as brothers. Each girl has twice as many brothers as sisters. How many children are there?
7 children (4 boys and 3 girls).
A clock loses 10 minutes every 24 hours. If it is set right at 8:00 AM, what time will it show at 8:00 AM the next day?
7:50 AM
A girl sells oranges. She sells half her oranges plus half an orange to 3 straight buyers, leaving her with zero. She didn't cut any oranges. How many did she start with?
7 oranges
I drove to a bridge at 25 mph due to heavy traffic rush, but drove home smoothly at 50 mph. What was my average speed for the whole round trip?
33.3 mph (not 37.5!).
Arrange all 9 digits (1 to 9) to form four separate perfect square numbers.
9, 81, 324, and 57
A man is twice as old as his wife was when he was as old as she is now. Combined, they are 42. How old are they?
The husband is 24 and the wife is 18.
How many times do the minute hand and the hour hand of a clock cross past each other in a single 24-hour day?
22 times
A traveler buys an item for $7, sells it for $8, buys it back for $9, and sells it again for $10. How much total profit did they make?
$2 profit.
Two birds fly toward each other from two trees 100 meters apart. One flies at 10m/s, the other at 15m/s. A fly zips back and forth between them at 20m/s until they meet. How far did the fly travel?
80 meters (it flew for 4 seconds).