# NCERT Class 9 Solutions: Surface Areas and Volumes (Chapter 13) Exercise 13.1 – Part 3 (For CBSE, ICSE, IAS, NET, NRA 2022)

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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 ₹ , 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 ₹ 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 = = = = =