Xavier Aptitude Test 2022 Paper

The total number of ways of selecting 3 notes from the :
five 10-rupee notes, three 20-rupee notes, and two 50-rupee notes $=10\mathrm{notes}$ in total.
$10{\mathrm{C}}_3=120$
The possibilities for the value of the three notes combined is at least 90 :
$\mathrm{Rs}50+\mathrm{Rs}20+\mathrm{Rs}20$:
The possibilities for this selection is :
$2{\mathit{C}}_1.3{\mathit{C}}_2$
Selection of one Rs 50 note from the two and selection of 2 Rs 20 notes from the three.
$\mathrm{Rs}50+\mathrm{Rs}50+\mathrm{Rs}10$:
$2{\mathit{C}}_2.5{\mathit{C}}_1$
: Selection of two Rs 50 notes from the two and selection of 1 Rs 10 notes from the five.
$\mathrm{Rs}50+\mathrm{Rs}50+\mathrm{Rs}20$ :
$2{\mathit{C}}_2.3{\mathit{C}}_1$
Selection of two Rs 50 notes from the two and selection of 1 Rs 20 notes from the three.
A total of $6+5+3=14$ possibilities
The probability is $\frac{14}{120}$
$=\frac{7}{60}$