What English word has three consecutive double letters?

Replace the question mark with the correct number below.

I am a seven-letter word but if you remove four of my letters I will have one left. What word am I?

Name a key which is hardest to turn.

1 dollar = 100 cent
= 10 cent x 10 cent
= 1/10 dollar x 1/10 dollar
= 1/100 dollar
= 1 cent

=> 1 dollar = 1 cent

solve this tricky problem?

Which flower has two lips?

Take away my first letter, then take away my second letter. Then take away the rest of my letters, yet I remain the same. What am I?

In the addition below, all digits have been replaced by letters. Equal letters represent equal digits and different letters represent different digits.
ABCABA
BBDCAA
ABEABB
ABDBAA
------- +
AAFGBDH
What does the complete addition look like in digits?

Can you write down eight eights so that they add up to one thousand?

You need to arrange three 7 and mathematical symbols to form number 1?