Last updated at March 3, 2017 by Teachoo

Transcript

Ex 13.1, 7 Shanti Sweets Stall was placing an order for making cardboard boxes for packing their sweets. Two sizes of boxes were required. The bigger of dimensions 25 cm × 20 cm × 5 cm and the smaller of dimensions 15 cm × 12 cm × 5 cm. For all the overlaps, 5% of the total surface area is required extra. If the cost of the cardboard is Rs 4 for 1000 cm2, find the cost of cardboard required for supplying 250 boxes of each kind. For bigger box Length of bigger box = 25 cm Breadth of bigger box = 20 cm Height of bigger box = 5 cm Total surface area of bigger box = 2(lb + lh + bh) = [2(25 × 20 + 25 × 5 + 20 × 5)] cm2 = [2(500 + 125 + 100)] cm2 = 1450 cm2 Extra area required = 5% × Surface Area of bigger box = 5/100 × 1450 = 72.5 cm2 Total area required for 1 bigger box = Total Surface Area + Extra area required = (1450 + 72.5) cm2 = 1522.5 cm2 Total area required for 250 box = Area of 1 box × 250 = (1522.5 × 250) cm2 = 380625 cm2 For smaller box Length of smaller box = 15 cm Breadth of smaller box = 12 cm Height of smaller box = 5 cm Total surface area of smaller box = 2(lb + lh + bh) = [2(15 ×12 + 15 × 5 + 12 × 5] cm2 = [2(180 + 75 + 60)] cm2 = (2 × 315) cm2 = 630 cm2 Extra area required = 5% × Surface Area of smaller box = 5/100 × 630 = 31.5 cm2 Total area required for 1 smaller box = Surface Area + Extra Area = (630 + 31.5) cm2 = 661.5 cm2 Area of cardboard sheet required for 250 such smaller boxes = Total area × 250 = (250 × 661.5) cm2 = 165375 cm2 Total cardboard sheet required = Area of 250 big box + Area of 250 smaller box = (380625 + 165375) cm2 = 546000 cm2 Cost of 1000 cm2 cardboard sheet = Rs 4 Cost of 1 cm2 cardboard sheet = Rs 1/1000 × 4 Cost of 546000 cm2 cardboard sheet = Rs ((546000 × 4)/1000) = Rs 2184 Therefore, the cost of cardboard sheet required for 250 such boxes of each kind will be Rs 2184.

Chapter 13 Class 9 Surface Areas and Volumes

Example 2
Important

Ex 13.1, 6 Important

Ex 13.1, 7 Important You are here

Ex 13.2, 3 Important

Ex 13.2, 4 Important

Ex 13.2, 9 Important

Example 6 Important

Ex 13.3, 3 Important

Ex 13.3, 5 Important

Ex 13.4, 3 Important

Ex 13.4, 8 Important

Ex 13.4, 9 Important

Ex 13.5, 6 Important

Ex 13.5, 8 Important

Ex 13.5, 9 Important

Example 14 Important

Ex 13.6, 3 Important

Ex 13.6, 7 Important

Ex 13.7, 5 Important

Ex 13.7, 6 Important

Ex 13.7, 7 Important

Ex 13.7, 8 Important

Example 18 Important

Ex 13.8, 4 Important

Surface Area and Volume Formulas Important

Class 9

Important Questions for Exam - Class 9

- Chapter 1 Class 9 Number Systems
- Chapter 2 Class 9 Polynomials
- Chapter 3 Class 9 Coordinate Geometry
- Chapter 4 Class 9 Linear Equations in Two Variables
- Chapter 5 Class 9 Introduction to Euclid's Geometry
- Chapter 6 Class 9 Lines and Angles
- Chapter 7 Class 9 Triangles
- Chapter 8 Class 9 Quadrilaterals
- Chapter 9 Class 9 Areas of parallelograms and Triangles
- Chapter 10 Class 9 Circles
- Chapter 11 Class 9 Constructions
- Chapter 12 Class 9 Herons Formula
- Chapter 13 Class 9 Surface Areas and Volumes
- Chapter 14 Class 9 Statistics
- Chapter 15 Class 9 Probability

About the Author

Davneet Singh

Davneet Singh is a graduate from Indian Institute of Technology, Kanpur. He has been teaching from the past 8 years. He provides courses for Maths and Science at Teachoo. You can check his NCERT Solutions from Class 6 to 12.