We have:

25 do not divide to 10

So 25 can't be true about number N of doors .

Note: I'm not certain

Hà Đức Thọ            

1) The odd numbers is sorted into rows below:

1

3     5

7     9     11

13     15     17    19    

21     23     25     27     29

...       ...      ...      ...      ...     ...     ...

What is the sum of the numbers in row 20?

(MYTS - 2018 - Grade 7)

(#1000: 1000 best IQ question in history)

Two mathematician met each other in a flight to Moscow.

You have 3 children, don't you. How old are they now? - Ivan asked.

Their ages product is 36 and their ages sum is exactly the date of today! The other mathematician said.

After thinking for a while, Ivan said: Sorry but I need more info.

"Oh, I forgot. The biggest child has a red hair."

"Now I know." Can you guess what their age is?

thanks

1. If you burn rubbish, you will produce harmful smoke.

 2. If you reuse these bottles, you will save a lot of money.

 3. If students use recycled paper, they will save a lot of trees.

 4. If students plant trees in the schoolyard, their school will be a greener place.

 5. If there is a rubbish bin in every class, the classroom will be cleaner.

1. take               2. will save            3. cycle           4. will be            5. cycle                      6. won't produce
7. aren’t            8. will be                9. plant            10. won't be       11. don't hurry          12. will be