then (n, r)=

 then ‘n’ is

If  = mC₂, then C₂ is equal to -

Students must know how to open expressions like nCr.
Also, the value of n! is n.(n−1).(n−2).....3.2.1.
Combination is used to select r objects from n objects when the arrangement of the objects does not matter.

Twelve students compete for a race. The number of ways in which first three places can be taken, is-

Given the circuit :

Which of the following is equivalent to the above circuit ?
I)
II)
The true statement in the above is / are

The symbolic form of logic of the circuit given below is

The following circuit when expressed in the symbolic form of logic is

For conversion C(graphite)→C(Diamond),the DS is-

Consider the following processes: DH(kJ/mol) ½A→B +150 3B→2C+D–125 E+A→2D+350 ForB+D→E+2C,DHillbe-

Enthalpy change for the reaction, 4H_(g) →2H_2(g) is–869.6kJ The dissociation energy of H–H bond is

ThevaluesofDHandDSforthereaction,C(graphite)+CO(g)→2CO(g)are170kJand170 JK–1respectively.Thisreactionwillbespontaneousat

Assertion: The sum of all4 digited numbers that can be formed using the digits 1,2,4,5,6 without repetition is 479952
Reason: Sum of all ‐digit numbers formed by taking the given n digits (without zero) is (sum of all the n digits) ( times).

Assertion: There are three doors to a room The number of ways in which a student can enter the room and leave it by a different door is 6.
Reason: If an operation can be performed in ways and another operation can be perfO rmed in ways thenthe two operations in succession can be performed in mn ways.

Assertion(A): The number of quadratic expressions with the coefficients drawn from the set {0,1,2,3} is only 48 but not 64.
Reason(R): The coefficient inthe quadratic expression can not be ’

Assertion (A) : The number of ways of arranging 6 boys and 5 girls alternately at circular table is Reason (R) : To arrange boys and girls alternately at a circular table, they should be equal in number.

GivenenthalpyofformationofCO2(g)andCaO(s) are–94.0KJand–152KJrespectivelyandthe enthalpyofthereaction-CaCO3(s) →CaO(s)+CO2(g) is42KJ.The enthalpyofformationofCaCO3(s)