The magnitude of two forces, which when acting at right angle produce resultant force of $$\sqrt {10} $$  kg and when acting at 60° produce resultant of $$\sqrt {13} $$  kg. These forces are

correct option is B

3 and 1

Here v10 means root 10
So its square is 10
v13 means root 13
So its square is 13

Now refer to Muhammad Saqib's answer

Mohammad saqib why aren't you using square of resultant?

this is wrong answer.....right answer is 3kg and 1kg

Answer is wrong.it should be 3&1.

B. 3 and 1 kg

Given answer is incorrect
Let the forces be f1 and f2
f1²+f2²=10
as the angle between them is 90 degrees
when angle is 60
f1²+f2²+2*f1*f2*cos(60)=13
10+f1*f2=13
3=f1*f2
(f1+f2)²=f1²+f2²+2*f1*f2=10+6=16
f1+f2=4...(1)
f1-f2=√((f1+f2)²-4f1*f2)=2...(2)
from (1) and (2) u get
f1= 3 N f2= 1 N

How's the answer is coming?