When the teacher's heartbeat becomes faster | Amezing maths tricks for fast calculation #shorts

A teacher gave sum to his class to find the average of n numbers viz.1,2,3,4,5,6... etc. But when the teacher checked the solution,he has found that during the calculation a student just missed a number for the addition thus his average of the n numbers was 15. The value of n is:

A teacher gave sum to his class to find the average of n numbers viz. 1,2,3,4,5,6,… etc. but when the teacher checked the solution, he has found that during the calculation a student just missed a number for the addition thus his average of the n number was 15. The value of n is :

When 2 g of a gas A is introduced into an evacuated flask kept at 25^(@)C , the pressure is found to be 1 atm . If 3 g of another gas B is then heated in the same flask, the total pressure becomes 1.5 atm . Assuming ideal gas behaviour, calculate the ratio of the molecular weights M_(A) and M_(B) .

When 2 g of a gas A is introduced into an evacuated flask kept at 25^(@)C , the pressure is found to be 1 atm . If 3 g of another gas B is then heated in the same flask, the total pressure becomes 1.5 atm . Assuming ideal gas behaviour, calculate the ratio of the molecular weights M_(A) and M_(B) .

Two straight thin bars, one of brass and the other of steel are joined togethre side by side by short steel cross-pieces at 0^(@)C , one cm long the centre lines of the bars being one cm apart. When heated to 100^(@)C , the composite bar becomes bent into the arc of a circle. calculate the radius of this circle. alpha for brass =19xx10^(-6) per .^(@)C and alpha for steel =11xx10^(-6) per .^(@)C

Assertion (A) : When a catalyst is added to a reaction mixture in equilibrium the amount of the products increases. Reason (R) : The forward reaction becomes faster on adding the catalyst.

Two trains one moving at a speed of 30 mile/h and iother at 60 mile/h, approaching each other. When a faster train blows a whistle, the apparent friequency of the note head by an observer at rest behind the faster train is 1852 Hz. Calculate the frequency of note produced by faster train (Assume speed of sound to be 1100 ft/s)