What is financial infrastructure?

The network of banks, payment systems and stock markets that helps manage money

What are the main things a bank does?

Holds deposits and lends money as loans

How do banks make money?

They pay lower interest on deposits and charge higher interest on loans

Earning interest on previous interest as well as on the original amount

What is the parity of the sum of two odd numbers?

It is even, e.g. \(3 + 5 = 8\).

Can five odd numbers add up to 30? Why?

No — the sum of five odd numbers is odd, but 30 is even.

Write an expression that is always even.

\(2n\) (or \(48w - 2\)) is always even.

Which number must occupy the centre of a 1–9 magic square?

The number \(5\) must be at the centre.

What is the Virahanka–Fibonacci rule?

Each term is the sum of the two preceding terms; \(1,2,3,5,8,13,\dots\).

What comes after 34 in the sequence 1, 2, 3, 5, 8, 13, 21, 34?

It is \(55\), since \(21 + 34 = 55\).

What is a cryptarithm?

A puzzle where each letter stands for a digit and must be worked out.

Number Play

Class 7 Mathematics · Ganita Prakash Part 1 · Chapter 6

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CBSE Class 7 · Mathematics

8 chapters: lakhs and crores to fractions

Marks booster + cheatsheet: key concepts in 2 lines each, common traps
Triangle inequality, Ch 7
Angle pairs of parallel lines, Ch 5
Common traps, corrected
Magic squares and Virahāṅka numbers, Ch 6
Brahmagupta's fraction formulas, Ch 8

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CBSE Class 7 · MathematicsTrending

Five congruence conditions to equations

Marks booster + cheatsheet: key concepts in 2 lines each
Integer sign rules, Ch 2
HCF and LCM by prime factors, Ch 3
Multiplying and dividing decimals, Ch 4
Mean, median and outliers, Ch 5
Ruler-and-compass constructions, Ch 6

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Summary

This playful chapter explores numbers through puzzles, parity, grids and famous sequences. Parity is the property of being even or odd: even numbers can be paired with no leftover, odd numbers cannot. You learn rules such as even + even = even, odd + odd = even, even + odd = odd, and use them to decide quickly whether a situation is possible (five odd cards can never sum to the even number 30). Expressions can be designed to be always even \((2n)\), always odd \((2n-1)\), or either. You then build magic squares — grids where every row, column and diagonal share the same magic sum (for the numbers 1–9 the magic sum is 15 and the centre must be 5) — and generalise their structure with a centre letter \(m\). The chapter celebrates the Virahanka–Fibonacci sequence \(1, 2, 3, 5, 8, 13, 21, 34, \dots\), where each term is the sum of the previous two, discovered in Indian poetry centuries before Fibonacci. It ends with cryptarithms, puzzles where letters replace digits.

Parity of numbers and sumsDesigning even/odd expressionsMagic squares and the magic sumGeneralising a magic square with algebraVirahanka–Fibonacci sequence and cryptarithms

Key terms

Parity

The property of a number being even or odd.

Even number

A number that can be arranged in pairs with no leftover; of the form \(2n\).

Odd number

A number that cannot be arranged in pairs; of the form \(2n - 1\).

Magic square

A square grid where each row, column and diagonal add to the same magic sum.

Magic sum

The common total of every row, column and diagonal of a magic square.

Virahanka–Fibonacci sequence

The sequence \(1,2,3,5,8,13,21,\dots\) where each term is the sum of the two before it.

Cryptarithm

A puzzle in which digits are replaced by letters that must be decoded.

Extra questions & answers

Try one from this chapter

The parity of a number refers to whether it is:

Flashcards & interactive practice