NCERT Exemplar Solutions Class 8 Mathematics Solutions for Squares and Square Roots & Cubes and Cube Roots - Exercise in Chapter 3 - Squares and Square Roots & Cubes and Cube Roots

Question 129 Squares and Square Roots & Cubes and Cube Roots - Exercise

A king wanted to reward his advisor, a wise man of the kingdom. So he asked the wiseman to name his own reward. The wiseman thanked the king but said that he would ask only for some gold coins each day for a month. The coins were to be counted out in a pattern of one coin for the first day, 3 coins for the second day, 5 coins for the third day and so on for 30 days. Without making calculations, find how many coins will the advisor get in that month?


Total coins the advisor get at the end = 1 + 3 + 5 +…..

The coins order is in the series of odd natural number,

So, the number of terms (n) = 30


Sum of odd natural numbers = n^2

= 30^2

= 900

∴ Total coins the advisor get at the end is 900.

Video transcript
hello guys hoping all of you are doing well and uh i'm lido tutor niha jangit today we'll be taking up this maths question which says the area of a rhombus is 84 square centimeter okay so we know the area like this area that is 84 square centimeter and we know its perimeter to be 56 centimeter and what we need to find out we need to find out its height all right so uh like area of rhombus that is 84 centimeter square in perimeter that is uh 56 centimeter this is all that we have been given also we need to uh like we need to understand that the specialty of rhombus is that first of thing all the sides are what equ as in the all the sides of our rhombus are equal so here if like a is the measurement of the one side then perimeter of this would be a plus adding up a 4 times that would come out to be 4 4a okay so we can say parameter of rhombus is 4 into its side so here we can see 56 centimeter which we have been already given in the question also uh if we want to find the side then we can what we can do is we can divide parameter by 4 right so we can obtain the one of these side so here we have 56 which uh 56 centimeter which is the perimeter upon 4 which is 14 centimeter all right so this is the side of the rhombus now uh like we need to find its height as well now we need to understand that area of rhombus can be found in like two ways first is like we can find its area by like uh by like having the product of diagonals and dividing that product with two okay that is half of products of diagonals this is the first way and the second way is to find the product of base and its distance from the opposite side okay that is base into height so this is the way second one is the way that will make use of all right so let's get started so here we have area of rhombus as base into height okay so here uh like if we want to find the height what we'll do is we'll divide this uh area with base okay so we are dividing this area of rhombus with base and let us see what comes out to be therefore height will come out to be area of rhombus that is 84 okay 84 centimeter square upon 14 centimeter which gives us 6 centimeter okay and here the height is six centimeter so this is the answer of this question if still any doubts persist so you can mention that in the comment section below and we'll help you out okay so have a wonderful day ahead thank you
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