# NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.1 – Part 3

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Q-6 A small indoor greenhouse (herbarium) is made entirely of glass panes (including base) held together with tape. It is long, wide and high.

What is the area of the glass?

How much of tape is needed for all the ?

Solution:

Solution (i)

Dimensions of greenhouse are

Total surface area of greenhouse are the areas of its 6 faces (3 faces each appear twice on opposite sides) =

Solution (ii)

Length of the tape needed is the length of all its edges. Note that all the edge lengths appear 4 times (2 times on opposite sides of each face with a similar face appearing on opposite side of a the cube). Therefor the total length of all the edges =

Q-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 and the smaller of dimensions 1. For all the overlaps, of the total surface area is required extra. If the cost of the cardboard is Rs. , find the cost of cardboard required for supplying boxes of each kind.

Solution:

Dimension of bigger box . Therefore, total surface area of 1 bigger box (area of all the faces) =

=

=

=

=

Dimension of smaller box , therefore, total surface area of smaller box =

=

=

=

=

Therefore total surface area of boxes of each type =

The overlaps require 5% extra area, therefore extra area required

Total Cardboard required

One cardboard sheet has area . Therefore the number of sheets required = . Cost of 1 sheet is 4 Rs. Therefore, total cost of 546 cardboard sheet

Q-8 Parveen wanted to make a temporary shelter for her car, by making a box-like structure with tarpaulin that covers all the four sides and the top of the car (with the front face as a flap which can be rolled up). Assuming that the stitching margins are very small, and therefore negligible, how much tarpaulin would be required to make the shelter of height 2.5 m, with base dimensions 4m × 3m?Solution:

There is no top, so tarpaulin is only required for the four sides and top. Therefore, Tarpaulin required = = = = =