JEE Main 26 Feb 2021 Shift 2 Solved Paper

Given, f=340Hz
Let beat frequency of tuning fork A is fA
and fA′ be the frequency of tuning fork A after filling.
In first case, beat frequency =5
⇒‌fA=340±5
⇒‌fA=345Hz‌ or ‌335Hz
After filling tuning fork A,fA′=340±2
⇒‌‌fA′=342‌ or ‌338Hz
As on filling, frequency of A increases.
Hence, original frequency of tuning fork A is 335Hz.