{tocify} $title={এক নজরে শিরোনাম}
- income = expenditure + saving
- if a,b is given number so third proportional to a and b is = b2/a
- if a,b,c is given number so fourth propotional to a,b,c = (b⨯c)/a
- simple interest (SI) = PRT / 100
- area of walls = 2 h (l+b) [h=height, l=length, b=breadth] unit in sq.m
- speed = distance / time
- speed of boatman = (speed of upstream + speed of downstream) / 2
- average speed = total distance / total time
- if some fraction are given so HCF of fractions = HCF of nemerators / LCM of denominators
- profit = sp - cp [cp=cost price, sp=selling price]
- profit % = (profit / cp) ⨯ 100
- area of trapezium = 1/2 ⨯ sum of parallel sides ⨯ height
- volume of cylinder = πr2h
- total surface area of cylinder = 2πr(r+h)
- am ⨯ an = am+n
- (x)1/2 is same to √x Example. (4)1/2 = √4 = 2