Why is a river so rich ?

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

What Word am I Looking For ?

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?

Our product and our sum always give the same answer. Who are we?

Chocolate costs 6 rupees and a Toy costs 5 rupees. If you have 32 rupees in total, how many chocolates and how many Toys can be purchased with that amount?

Lady Gaga is pregnant and currently has 6 daughters

1. Dorry 2. Rebeka 3. Michael 4. Faniya 5. Sophia 6. Lavanya

What will she name her next child girl? (Think Logical)

A. Neema B. Tanya C. Tisha D. Jenniffer

What does man love more than life, and hate more than death or mortal strife; that which satisfied men want; the poor have, and the rich require; the miser spends, the spendthrift saves, and all men carry to their graves?

Twice ten are six of us,

Six are but three of us,

Nine are but four of us;

What can we possibly be?

Would you know more of us?

Twelve are but six of us,

Five are but four, do you see?

What are we?

There were three women in all the swimming costumes!
One was happy and the other two were sad!
The happy one was crying and the sad ones were smiling.
Why was this?

It is a nine-letter word.
The exact opposite of the phrase "friendly and outgoing"
It contains the word "over".
It starts will a vowel.

What is it?