web analytics

Example 6 - A corn cob, shaped somewhat like a cone - Area Of Cone

  1. Chapter 13 Class 9 Surface Areas and Volumes
  2. Serial order wise
Ask Download

Transcript

Example 6 A corn cob (see Fig. ), shaped somewhat like a cone, has the radius of its broadest end as 2.1 cm and length (height) as 20 cm. If each 1 cm2 of the surface of the cob carries an average of four grains, find how many grains you would find on the entire cob. We know that grains are on the curved surface Area First we find the area of corn cob which is in the form of a cone. Curved Surface Area of corn cob = πrl r = 2.1 cm, h = 20cm Let slant height be l We know that l2 = h2 + r2 l2 = "(20)2 + (2.1)2" l2 = "400 + 4.4" 1 l2 = "40" 4.41 l = √("40" 4.41) l = √("20.112" ) l = 20.11 cm Now, Area of corn cob = Curved Surface area of cone = πrl = 22/7 × 2.1 × 20.11 cm2 = 132.726 cm2 = 132.73 cm2 (approx.) Number of grains on 1 cm2 of the surface of corn cob = 4 Number of grains on 132.73 cm2 of the surface of corn cob = 132.73 × 4 = 530.92 = 531 (approx) So, there would be approximately 531 grains of corn on the cob.

About the Author

CA Maninder Singh's photo - Expert in Practical Accounts, Taxation and Efiling
CA Maninder Singh
CA Maninder Singh is a Chartered Accountant for the past 8 years. He provides courses for Practical Accounts, Taxation and Efiling at teachoo.com .
Jail