I am looking for a word that change both gender and number when i add the letter 'S'.

What Word am I Looking For ?

When my father was 31 I was 8. Now he is twice as old as me. How old am I?

A wooden log balances equally on the scales when weighed with three-quarters of a pound and three-quarters of a wooden log.

Can you calculate the weight of the entire wooden log?

Count the number of times the letter "F" appears in the following paragraph:

FAY FRIED FIFTY POUNDS OF
SALTED FISH AND THREE POUNDS
OF DRY FENNEL FOR DINNER FOR
FORTY MEMBERS OF HER FATHER'S FAMILY.

I am a normal creature, but I have five hands. I can even have more but even then I will be considered normal.

Who am I?

A person was found dead on a big green land with no trees or buildings around. When the police arrived, they found a piece of rock lying next to him and the man was wearing clothes comprising of red, blue and yellow colours.

Can you tell who the person is and what was the cause of death?

What are the five permanent members of the UN Security Council?

a) France, Germany, Italy, Japan, United Kingdom
b) Canada, Mexico, Saudi Arabia, Turkey, United Arab Emirates
c) Brazil, India, Nigeria, South Africa, South Korea
d) China, France, Russia, United Kingdom, United States

Lifeless eyes on my smiling face and watch your child's sleeping place. In their dreams they hold me tight. What am I?

It can be easily calculated that the digits 0 to 9 can be arranged into 3628800 distinct ten-digit numbers.

But do you know how many of these numbers are prime?

What can run but never walk, have a mouth that never speaks, have a head that never weeps, and have a bed but never sleeps?