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→Hints for difficult problems
= Hints for difficult problems =
= Hints for difficult problems =
Craft teacher of a school taught the students to prepare cylindrical pen holders out of card board. In a class of strength 42, if each child prepared a pen holder of radius 5 cm and height 14 cm, how much cardboard was consumed?
==Mensuration==
Exercise 16.1<br>Problem 7.
1)Craft teacher of a school taught the students to prepare cylindrical pen holders out of card board. In a class of strength 42, if each child prepared a pen holder of radius 5 cm and height 14 cm, how much cardboard was consumed?
Statement of the problem: How much cardboard was consumed to prepare 42 cylindrical pen holders each of radius 5 cm and height 14 cm.
*Interpretation;
Case 1)Pen stand which is open on top and closed base.
Then we have to calculate Curved surface area of cylinder and area of one circle.
*skills
visualising the cylinder into rectangle and circle
*Assumptions:
Concepts used
#basics of circles -radius
# area of circles
# addition and multiplication of fractions
#unit of area
knowledge to be used
#knowledge of Polygons -Rectangles
# knowledge of measurements
#Formula of CSA of cylinder
#substitution
#computing
#Value of Л
Concepts to be taught
#basics of circles -radius
# area of circles
#relation between circumference of circle and length of rectangle in a cylinder
# addition and multiplication of fractions
#unit of area
solution: r=5cm, h=14cm, Л=
Curved surface area of cylinder and area of one circle= CSA of cylinder+area of circle
=2Лrh+ Л
= 2XX5X14+X
=440+78.5
=518.5
Cardboard required to prepare 42 penstands= 42X518.5=21777
=2.1777
Case 2:- Hollow pen stand: Pen stand which is open both the sides i.e., top and base.
Then we have to calculate Curved surface area of cylinder.
Case 3:-Pen stand which is closed both the sides i.e., top and base.
Then we have to calculate total surface area of cylinder.
Activity
Making use of 2200 cmcardboard sheet how many hollow cylinders of radius 7 cm and height 5 cm can be prepared.
2)Find the weight of a solid cone whose base is of diameter 14 cm and vertical height 51,
cm, if the material of which it is made weighs 10gm/
*Statement of the problem:What is the weight of a solid cone whose base is of diameter 14 cm and vertical height 51cm, if the material of which it is made weighs 10gm/
*Interpretation;
Calculating the weight of solid cone by calculating its volume.
density of a material is given. it is related to volume and weight.
* Assumptions:
Concepts used
#basics of circles -radius
# area of circles
# multiplication of fractions
#unit of volume,density and weight
#density
knowledge to be used
#radius=
#density=
# knowledge of measurements
#Formula of volume of cones
#substitution
#computing
#Value of Л
Concepts to be taught
#density
#units conversion
solution:
d=14cm r===7cm, h=51cm
Volume of cone=Лh
=XX7X7X51=2618
To calculate weight of the solid cone we have to use density of the given material.
density=10gm/
=Kg/
Weight of solid cone=volumeXdensity
=2618XKg/
=26.18Kg
= Project Ideas =
= Project Ideas =