Haryana Police Constable Model Paper 4

Given:
Six digits number is $25\mathrm{a}64\mathrm{b}$
Concept used:
Divisibility rule of 11, says, in a number when we add even place digits and subtract it from the sum of odd place digits, results will be either 0 or multiple of 11
Calculation:
In digits 25a64b, the sum of odd place digits $=2+\mathrm{a}+4$
$\Rightarrow 6+\mathrm{a}$
the sum of even place digits $=5+6+\mathrm{b}$
$\Rightarrow 11+\mathrm{b}$
According to the divisibility rule of 11,
The sum of odd place digits – the sum of even place digits = 0
$\Rightarrow 6+\mathrm{a}\mathit{–}\left(11+\mathrm{b}\right)=0$
$\Rightarrow \mathrm{a}\mathit{–}\mathrm{b}=11\mathit{–}6$
$\Rightarrow \mathrm{a}\mathit{–}\mathrm{b}=5$
∴ The value of (a – b) is 5.