I am the only even prime number. Multiply me by any whole number, and the product will always be even. What am I?

I am an even positive integer less than 100. Divided by 3, my remainder is 2. Divided by 5, my remainder is 4. Divided by 7, my remainder is 0. What number am I?

I am an angle whose measure is strictly greater than 90 degrees but strictly less than 180 degrees. What term describes me?

I am a two-digit prime number. If you reverse my digits, the new number is also prime, and the difference between us is 18. What number am I?

Using only a 3-gallon jug and a 5-gallon jug with unlimited water, how can you measure out exactly 4 gallons of water?

Using only addition, how can you add eight 8s together to get a total of 1,000?

A cloth bag holds 4 crimson marbles, 4 navy marbles, and 4 emerald marbles. Reaching in without looking, what is the minimum number of marbles you must pull out to guarantee at least two of the same color?