Question

There are four trees on which 5, 7, 4, and 9 birds are resting respectively. When a child arrived, he began counting the birds. The total number of birds the child will count resting on these 4 tress is .

Answer 1

Number of birds on tree $1=5$
Number of birds on tree $2=7$
Number of birds on tree $3=4$
Number of birds on tree $4=9$
Total number of birds on trees $=5+7+4+9$
For this grouping can be done as $=(5+7)+(4+9)$
$\Rightarrow (5+7)+(4+9)=12+13=25$
There were total 25 birds resting on trees.