Can you solve this tricky maths equation problem by replacing it? mark with the correct symbol?

19834 -----: 187
15921 -----: 153
17561 -----: 139
13734 -----: ???

How many pluses should we put between the digits of 987654321 to get a total of 99, and where?

What can go up a chimney down, but can’t go down a chimney up?

How many triangles are there in the picture below?

A high school has a strange principal. On the first day, he has his students perform an odd opening day ceremony:

There are one thousand lockers and one thousand students in the school. The principal asks the first student to go to every locker and open it. Then he has the second student go to every second locker and close it. The third goes to every third locker and, if it is closed, he opens it, and if it is open, he closes it. The fourth student does this to every fourth locker, and so on. After the process is completed with the thousandth student, how many lockers are open?

I am weightless, but you can see me. Put me in a bucket, and I'll make it lighter. What am I?

When is the top of a mountain similar to a savings account?

Can you think of a smallest +ve number such that if we shuffle the digits of the number, the new number becomes double the original number?

There is a square of a particular number which when doubled, becomes 7 more than its quarter.

Can you find the number?

I noticed one of the words in the oxford dictionary is spelled incorrectly. What about you?