Key Concepts

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  • Find the ratio of 5 m to 10 km
    = 5 m : 10 × 1000 m [∵ 1 km = 1000 m]
    = 5 m : 10000 m
    = 1 : 2000
  • Percent: By a certain percent we mean that many hundredths.

x % = x hundredths = x/100

  • Convert the following ratios to percentages:
    (a) 3 : 4
    (b) 2 : 3
    Solution:
    NCERT Solutions for Class 8 Maths Chapter 8 Comparing Quantities Ex 8.1 Q2
  • Finding the increase percent 

  • Finding the decrease percent 

  • Selling ( Profit/Loss/Discount) 

, ,

,

  • Billing Amount =  Original Price + (  Sales Tax/VAT/GST)
  • Selling Price if ( Sales Tax/VAT/GST ) is added on cost price.

  • Simple Interest Formula:

  • Amount after n years is given by

where P = Principal Amount  , R = Rate per annum compounded annually , n=Number of years.

  • Compound interest = (amount) - (principal).

CI = A - P

  • If the rates be p%, q% and r% during the 1st, 2nd and 3rd years respectively then amount after 3 years
  • If principal = Rs P, rate = R% per annum and time = n years then
    (i) Amount after n years (compounded annually)

(ii) Amount after n years (compounded half-yearly)

  • To find CP when SP and gain% or loss% are given:

 

 

 

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