Solution: 5. The original radius of the circular site is: root number (37.68/2x3. 14) = 6m,

Therefore, the area increased by widening the site is:

3.14x [(6+1) 2-62] = 40.82 square meters.

6。 Meaning from the title: the radius of the largest semicircle is 2cm,

So the circumference of the largest half circle is: 3.14x2+2x2 =10.28cm,

The area of the largest semicircle is: (1/2) x 3.14x2 2 = 6.28cm2.

7。 Grandpa Wang knows that the circumference of the round table is 212+102 = 314cm after measurement.

Then calculate the area from the perimeter.

The area of this desktop is: 3142/(4x3.14) = 78.5cm.