How do you use mental math to find the sum or product and then identify the property or properties that you use to simplify (27+8)+12?

Give chapter 5 lines and angles own questions for board exams 

Find the following percentage value:

1) 15% of 250.

Find the angle which is equal to its supplement.

Find the breadth of the rectangle whose length is 70 cm and perimeter 200 cm.

Convert 1 gallon into liters.

a. 3.05 liters

b. 3.78 liters

c. 4.05 liters

d. 4.78 liters