NCERT Solutions Ganita Prakash (Part 1) Chapter 2 .5 A Pinch of History — In-text Questions

Book page 432 Updated on2026-09-05

Q1.
What does the first part of each name denote? [million (10⁶), billion (10⁹), trillion (10¹²), quadrillion (10¹⁵), quintillion (10¹⁸), sextillion (10²¹), septillion (10²⁴), octillion (10²⁷), nonillion (10³⁰), decillion (10³³)]
Answer

It is a counting word, and it tells you how many times 1000 is multiplied into 1000.

NameFirst part meansBuilt asValue
million1 (Latin mille, thousand)1000 × 1000106
billionbi = 21000 × 10002109
trilliontri = 31000 × 100031012
quadrillionquadri = 41000 × 100041015
quintillionquint = 51000 × 100051018
decilliondec = 101000 × 1000101033
If the first part stands for k, the name equals 1000 × 1000k = 103 × 103k = 103k+3
Check: k = 3 (trillion) gives 109+3 = 1012
Why it happens: the whole family is generated by one rule — each name is 1000 times the one before, so the exponents rise in steps of 3. The Indian names work the same way but step by 100 instead: lakh 105, crore 107, arab 109, kharab 1011, neel 1013, padma 1015, shankh 1017, maha shankh 1019 — exponents rising by 2 each time.
Did you know? In the Lalitavistara (first century BCE) the mathematician Arjuna names odd powers of ten all the way to a tallakshana, 1053. A Pali grammar treatise of Kāccāyana goes to 10140, called asaṅkhyeya.
Q2.
The currency note with the highest denomination in India currently is 2000 rupees. Guess what is the highest denomination of a currency note ever, across the world.
Answer

The record is the 1 sextillion pengő note — 1021 pengő, also called 1 milliard bilpengő — printed in Hungary in 1946, though it was never issued.

NoteFace valueIn standard form
₹2000 (India)20002 × 103
100 trillion Zimbabwean dollars (2009)1,00,000,000,000,0001014
1 sextillion pengő (Hungary, 1946)1 followed by 21 zeros1021
Pengő note ÷ ₹2000 note = 1021 ÷ (2 × 103)
= 0.5 × 1018 = 5 × 1017 times the face value
Why it happens: such notes appear when prices are themselves growing exponentially — during hyperinflation prices multiply, they do not merely add, so the government must keep adding zeros to keep up. The Zimbabwean 100 trillion dollar note was worth about $30 when it was printed, which shows how quickly the printed number and the real value part company.
Did you know? 10100 has its own name, a googol. The estimated number of atoms in the universe is only 1078 to 1082 — so a googol is larger than the count of everything there is.
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