Question

A force of 5 N gives a mass m1, an acceleration of 10 m s–2 and a mass m2, an acceleration of 20 m s-2. What acceleration would it give if both the masses were tied together?
NCERT Class IX
Sciences - Main Course Book
Chapter 9. Force and Laws of Motion

Answer 1

when a force of 5N gives an acceleration of 10ms-² to a body 
then its mass = 5/10 kg = 0.5kg
so, m₁ = 0.5kg

when a force of 5N gives an acceleration of 20ms⁻² to a body 
then its mass = 5/20 kg = 0.25kg
so, m₂ =  0.25kg
when the two bodies r tied total mass of the system bcomes = 0.75kg
so acceleration of the system will b = force/mass = 5/0.75 = 6.67 ms⁻²

I hope its help you.