Model of surface area &volume

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Compound Interest class 8 chapter6(notes) maths definition, formula

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Compound Interest Definition Compound interest is the interest calculated on the principal and the interest accumulated over the previous period. It is different from the simple interest where interest is not added to the principal while calculating the interest during the next period. Compound interest finds its usage in most of the transactions in the banking and finance sectors and also in other areas as well. Some of its applications are: Increase or decrease in population. The growth of bacteria. Rise or depreciation in the value of an item. Compound Interest Formula The compound interest formula is given below: Compound Interest = Amount – Principal Where the  amount  is given by: Where, A= amount P= principal R= rate of interest n= number of times interest is compounded per year It is to be noted that the above formula is the general formula for the number of times the principal is compounded in an year. If the amount is compounded annually, the amount is given as-              
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Revision notes for class 10 & 9 CIRCLES

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Revision Notes on Circle The equation of a   circle   with its center at C(x 0 , y 0 ) and radius r is: (x – x 0 ) 2  + (y – y 0 ) 2  = r 2     If x 0  = y 0  = 0 (i.e. the centre of the circle is at origin) then  equation of the circle   reduce to x 2  + y 2  = r 2 . If r = 0 then the circle represents a point or a point circle. The equation x 2  + y 2  + 2gx + 2fy + c = 0 is the general equation of a circle with centre (–g, –f) and radius √(g 2 +f 2 -c). Equation of the circle with points P(x 1 , y 1 ) and Q(x 2 , y 2 ) as extremities of a diameter is (x – x 1 ) (x – x 2 ) + (y – y 1 )(y – y 2 ) = 0.  For general circle, the equation of the chord is x 1 x + y 1 y + g(x 1  + x) + f(y 1  +y) + c = 0 For circle x 2  + y 2  = a 2 , the equation of the chord is x 1 x + y 1 y = a 2   The equation of the  chord  AB (A ≡ (R cos α, R sin α); B ≡ (R cos β, R sin β)) of the circle x 2  + y 2  = R 2  is given by x cos ((α + β )/2) + y sin ((α - β )/2) = a cos (
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