Question

When positive no is multiplied by a negative number why negative sign is given?

Answer 1

Let us first assume that
positive x negative = positive

Suppose a friend of you takes Rupees 3 from you for 2 days

Since Rs. 3 are being taken away from you so , for you the amount will be negative so every day you have -3 Rupees.

So, the total will be :
2 days * (-3) rupees = 6 rupees

This equation indicates that you have gained
6 rupees whereas you have given out
6 rupees . Hence the total will be negative .

So , our assumption that
positive x negative = positive
is false

So, now
2 days * (-7) rupees = (- 14) rupees

Hence positive x negative = negative