1) Equivalent Fractions-> Ratios which have the same
value in their simple form.
2) Ratios are just the fraction form to compare numbers.
For eg->
2
3
𝑖𝑠 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑎𝑠 2: 3.
3) Inversely proportion or a∝
1
𝑏
is when ‘a’ ratio increases
but ‘b’ ratio decreases. The same is when ‘a’ decreases
but ‘b’ increases.
4) Direct proportion or a∝b is when the ‘a’ ratio and ‘b’
ratio increase and decrease together.
5) Percentages are Fractions with 100 in denominator.
a. Fraction in Percent->
𝑎
𝑏
× 100=P%
b. Decimal to Percent->D× 100=P%
c. Percent to Fraction->
𝑃
100
=
𝑎
𝑏
d. Percent to Decimal->
𝑃
100
= 𝐷
e. Ratio to Percent->1: 3 𝑖𝑛 𝑝𝑒𝑟𝑐𝑒𝑛𝑡 = 1𝑥 + 3𝑥 = 4𝑥
then,
1𝑥
4𝑥
× 100 = 25%. 𝑆𝑎𝑚𝑒 𝑓𝑜𝑟 3𝑥. 1: 3 =
25%: 75%.
6) Per cent is derived from Latin word ‘per centum’
meaning ‘per hundred’.
7) Percentage of increase and decrease-
>
𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑐ℎ𝑎𝑛𝑔𝑒
𝑂𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡
× 100
8) Loss and Profit formulas->
a. Profit%=
𝑃
𝐶𝑃
× 100
b. Loss%=
𝐿
𝐶𝑃
× 100
c. Profit= SP-CP
d. Loss=CP-SP
e. CP=SP-Profit or SP+Loss
f. SP=CP+Profit or CP-Loss
g. CP=
𝑆𝑃×100
100−𝐿%
or
𝑆𝑃×100
100+𝑃%
h. SP=
100−𝐿%
100
× CP or
100+𝑃%
100
× CP
9) Simple Interest formulas->
a. SI=
𝑃×𝑅×𝑇
100
b. Amount=SI+P
c. SI=Amount-P
d. P=Amount-SI
e. P=
100×SI
𝑅×T
f. R=
100×SI
𝑃×T
g. T=
100×SI
𝑃×R

Class 7 Chapter 8 Maths Comparing Quantities Notes (NCERT)

  • 1.
    1) Equivalent Fractions->Ratios which have the same value in their simple form. 2) Ratios are just the fraction form to compare numbers. For eg-> 2 3 𝑖𝑠 𝑡ℎ𝑒 𝑠𝑎𝑚𝑒 𝑎𝑠 2: 3. 3) Inversely proportion or a∝ 1 𝑏 is when ‘a’ ratio increases but ‘b’ ratio decreases. The same is when ‘a’ decreases but ‘b’ increases. 4) Direct proportion or a∝b is when the ‘a’ ratio and ‘b’ ratio increase and decrease together. 5) Percentages are Fractions with 100 in denominator. a. Fraction in Percent-> 𝑎 𝑏 × 100=P% b. Decimal to Percent->D× 100=P% c. Percent to Fraction-> 𝑃 100 = 𝑎 𝑏 d. Percent to Decimal-> 𝑃 100 = 𝐷 e. Ratio to Percent->1: 3 𝑖𝑛 𝑝𝑒𝑟𝑐𝑒𝑛𝑡 = 1𝑥 + 3𝑥 = 4𝑥 then, 1𝑥 4𝑥 × 100 = 25%. 𝑆𝑎𝑚𝑒 𝑓𝑜𝑟 3𝑥. 1: 3 = 25%: 75%. 6) Per cent is derived from Latin word ‘per centum’ meaning ‘per hundred’. 7) Percentage of increase and decrease- > 𝐴𝑚𝑜𝑢𝑛𝑡 𝑜𝑓 𝑐ℎ𝑎𝑛𝑔𝑒 𝑂𝑟𝑖𝑔𝑖𝑛𝑎𝑙 𝑎𝑚𝑜𝑢𝑛𝑡 × 100 8) Loss and Profit formulas-> a. Profit%= 𝑃 𝐶𝑃 × 100 b. Loss%= 𝐿 𝐶𝑃 × 100 c. Profit= SP-CP d. Loss=CP-SP
  • 2.
    e. CP=SP-Profit orSP+Loss f. SP=CP+Profit or CP-Loss g. CP= 𝑆𝑃×100 100−𝐿% or 𝑆𝑃×100 100+𝑃% h. SP= 100−𝐿% 100 × CP or 100+𝑃% 100 × CP 9) Simple Interest formulas-> a. SI= 𝑃×𝑅×𝑇 100 b. Amount=SI+P c. SI=Amount-P d. P=Amount-SI e. P= 100×SI 𝑅×T f. R= 100×SI 𝑃×T g. T= 100×SI 𝑃×R