📘 Unit 1: My Number World — Answer Key (Class 5 Maths Magic)
Page 4 — Do These (Lakh Names)
4,00,000 – Four lakh | 5,00,000 – Five lakh | 6,00,000 – Six lakh
7,00,000 – Seven lakh | 8,00,000 – Eight lakh | 9,00,000 – Nine lakh
4,50,000 – Four lakh fifty thousand
7,49,192 – Seven lakh forty nine thousand one hundred and ninety two
Do these:
1) 3,51,645 – Three lakh fifty one thousand six hundred and forty five
9,38,715 – Nine lakh thirty eight thousand seven hundred and fifteen
2) (Open-ended) Example: 74,930 → Seventy four thousand nine hundred and thirty (any 5 six-digit numbers using 7,4,9,3 with a digit repeated are acceptable)
Read the following:
20,00,000 – Twenty lakh | 30,00,000 – Thirty lakh | 40,00,000 – Forty lakh
50,00,000 – Fifty lakh | 60,00,000 – Sixty lakh | 70,00,000 – Seventy lakh
Do these:
1) 65,14,852 – Sixty five lakh fourteen thousand eight hundred and fifty two
29,36,429 – Twenty nine lakh thirty six thousand four hundred and twenty nine
2) (Open-ended) Example: 28,51 → any five 7-digit numbers using 2,8,5,1
Page 6 — Exercise-1
1) Biggest number: D) 7,96,581
2) Place value of 8 in 7,08,643: C) 8,000
3) Numbers in words:
a) 1,25,602 – One lakh twenty five thousand six hundred and two
b) 5,58,946 – Five lakh fifty eight thousand nine hundred and forty six
c) 9,57,524 – Nine lakh fifty seven thousand five hundred and twenty four
4) Numbers in figures:
a) Fourteen lakh thirty five thousand and fifteen = 14,35,015
b) Seventy four lakh sixty two thousand four hundred and sixty five = 74,62,465
5) Cost of house (₹45,87,000): Forty five lakh eighty seven thousand rupees
Cost of plot (₹18,56,000): Eighteen lakh fifty six thousand rupees
Total cost (₹64,43,000): Sixty four lakh forty three thousand rupees
Page 12–14 — Do These (Crore & Spike Abacus)
1) Standard form & words:
a) 7,21,594 – Seven lakh twenty one thousand five hundred and ninety four
b) 46,32,584 – Forty six lakh thirty two thousand five hundred and eighty four
2) Expanded form:
a) 40,63,52,456 = 40,00,00,000 + 0 + 60,00,000 + 3,00,000 + 50,000 + 2,000 + 400 + 50 + 6
b) 73,45,46,800 = 70,00,00,000 + 3,00,00,000 + 40,00,000 + 5,00,000 + 40,000 + 6,000 + 800 + 0 + 0
Note: Spike-abacus drawing questions and the "Activity-1(b)" bead-reading question depend on the exact bead counts shown in the printed image — please verify against the book figure before finalising the answer.
Do these (numeral → standard form):
a) Twenty five lakh five thousand eight hundred and forty one = 25,05,841
b) Five crore twenty lakh six thousand two hundred and five = 5,20,06,205
Expanded forms → standard form:
a) 60,00,000 + 0 + 50,000 + 1,000 + 0 + 0 + 8 = 60,51,008
b) 20,00,00,000 + 80,00,000 + 40,000 + 500 + 1 = 20,80,40,501
Page 16 — Exercise-2
1) (Depends on bead counts on the two abacus pictures — verify visually; typically compare total place values represented.)
2) Standard form:
a) 24536192 = 2,45,36,192
b) 900000100 = 90,00,00,100
3) In words:
a) 93,53,26,491 – Ninety three crore fifty three lakh twenty six thousand four hundred and ninety one
b) 70,30,10,400 – Seventy crore thirty lakh ten thousand four hundred
4) Expanded form:
a) 3,49,85,294 = 3,00,00,000 + 40,00,000 + 9,00,000 + 80,000 + 5,000 + 200 + 90 + 4
b) 50,23,80,050 = 50,00,00,000 + 0 + 20,00,000 + 3,00,000 + 80,000 + 0 + 0 + 50 + 0
5) Standard form:
a) Forty five lakh thirty three thousand six hundred and eighty four = 45,33,684
b) 5crore+20lakh+9lakh+40thousand+2thousand+1hundred+2ten+8one = 5,29,42,128
6) Distance Sun–Earth = 14,95,97,870 km
Expanded: 10,00,00,000 + 4,00,00,000 + 90,00,000 + 5,00,000 + 90,000 + 7,000 + 800 + 70 + 0
Page 20–21 — Exercise-3
1) Biggest 5-digit number (2,0,6,4,9): B) 96,420
2) Standard form of "fifty nine crore seventy lakh fifty eight thousand nine hundred and ten": A) 59,70,58,910
3) Place / place-value / face-value of underlined digits (verify exact underlined digit against the printed page):
a) 73,58,942 – if 5 is underlined: Place = Ten-thousands, Place value = 50,000, Face value = 5
b) 40,73,35,536 – if 3 (ten-thousand place) is underlined: Place = Ten-thousands, Place value = 30,000, Face value = 3
c) 82,45,63,125 – if 5 is underlined: Place = Lakhs, Place value = 5,00,000, Face value = 5
d) 64,63,98,524 – if 6 (first digit) is underlined: Place = Ten-crores, Place value = 60,00,00,000, Face value = 6
4) Digit to fill in 47,_5,63,251 for place-value 90,00,000 → digit = 9 (47,95,63,251)
Page 22 — Do These (Comparison & Ordering)
1) 87,83,93,790 > 8,29,80,758
2) 9,00,20,403 < 40,09,53,400
3) Ascending order: 10,29,47,026 ; 10,91,25,456 ; 1,93,85,702 ; 14,89,27,131 ; 64,34,68,735
4) Descending order: 98,43,26,834 ; 74,89,32,165 ; 48,29,30,456 ; 28,93,54,124 ; 6,95,39,821
Page 24 — Exercise-4
1) International standard form:
a) 4528973 = 4,528,973
b) 901247381 = 901,247,381
c) 200200200 = 200,200,200
2) Number names:
a) 1,200,000 – One million two hundred thousand
b) 7,521,256 – Seven million five hundred twenty one thousand two hundred and fifty six
3) a) 1 lakh = 100 thousands b) 1 million = 10 lakhs c) 1 crore = 10 millions
d) 1 hundred million = 10 crores e) 1 million = 1000 thousands
4) Place of digit 7 in 672,443,810: B) ten millions
5) One million = ______ thousands: C) 1000
Page 34 — Exercise-5 (Roman Numerals)
1) Roman numeral for 63: A) LXIII
2) LIV = B) 54
3) Convert to Roman: a) 7 = VII b) 78 = LXXVIII c) 56 = LVI
4) Convert to numbers: a) XII = 12 b) LX = 60 c) C = 100
5) Compare: a) LIII > XLIII b) LXX < LXXX c) LXXXIII = LXXXIII
6) Miswritten numeral: a) XXXXX (should be L) b) VV (V is never repeated)
7) Places we see Roman numerals: clock/watch faces, chapter or preface page numbers in books, sequel numbering (Part II, III), names of kings/popes (e.g., Henry VIII), Olympic Games numbering, building foundation-stone years.
Page 36 — Improve Your Learning
1) 40000 + ____ + 70 = 43070 → blank = 3000
2) Smallest number: a) 110 ones (=110)
3) NOT a correct expanded form of 3631: a) 3 + 6 + 3 + 1
4) For the number 5067:
a) It is an even number — F (False; 5067 is odd)
b) Place value of digit in thousands place is 100 — F (it is 5000)
c) Its nearest hundred is 5100 — T
d) Its predecessor is 5066 — T
5) 1 million in Hindu-Arabic system = 10,00,000 (ten lakh)
6) Rohan wrote 70 lakh as 7,000,000 (Seven Million). This is correct, because 1 million = 10 lakh, so 70 lakh = 7,000,000 = 7 million.
7) Preface ends on page "xiv" → page number = 14
8) Using digits 4, 6, 0, 8, 1, 3:
a) Greatest 6-digit number = 8,64,310; Smallest 6-digit number = 1,03,468 (0 cannot be the first digit)
b) Place value of 3 in the smallest number (1,03,468): 3 is in the thousands place → place value = 3,000
c) Reversing 1,03,468 → 8,64,301. Comparing with the greatest number 8,64,310: both match up to the tens place, but 8,64,301 < 8,64,310. So the new number is less than the original greatest number.
