Find the capacity (in litres) of a conical vessel with radius 7 cm and slant height 13 cm ? Give answer with explanation step by step please. Class-9th question
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Answers
Answer:
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Hint: Capacity of objects implies the volume of that object.
The given question can be directly solved by using the formula of the given object.
For reference, the volume of a cone =13πr2h cubic units=13πr2h cubic units .
Here, r is the base radius of the cone; h is the perpendicular height of the cone.
Assume π=227π=227 , unless stated otherwise.
Unit conversion can easily be done by the unitary method.
The unitary method is a technique for solving a problem by first finding the value of a single unit, and then finding the necessary value by multiplying the single unit value.
Complete step-by-step answer:
Step 1: Relation between base radius, slant height, and height of the cone
Let base radius of cone is denoted by r
The slant height of cone is denoted by l
And height of cone is denoted by h
Base radius and height fall perpendicular to each other, i.e., the angle between them is 90∘90∘.
Thus, a radius of length r cm, a height of length h cm, and a slant height of length l cm of the cone form a right-angled triangle.
Therefore, by applying Pythagoras theorem:
Pythagoras theorem: square of the hypotenuse is equal to the sum of the square of base and square of perpendicular.
In a right-angled triangle, the base and perpendicular are at the angle of 90∘90∘ each other and hypotenuse is the longest side.
Hypotenuse2 = Base2 + Perpendicular2Hypotenuse2 = Base2 + Perpendicular2
∵ slant height2=radius2+height2∵ slant height2=radius2+height2
⇒ l2=r2+h2⇒ l2=r2+h2
This relationship can be directly use if one of the parameter among l, r, and hl, r, and h is unknown.
Step 2: Volume calculations
Given that:
Radius, r = 7 cm
Slant height, l = 25 cm
For calculation of volume of cone base radius and height of cone should be known.
We know, l2=r2+h2 l2=r2+h2
⇒ 252=72+h2⇒ 625=49+h2⇒ h2=625−49=576⇒h=576−−−√