Number Play Class 7 Worksheet with Answers PDF | USP

Q42. A number game using divisibility. 4 (i) Write the smallest 5-digit number divisible by 9.

Ans: A+B+C=18; BC div by 4. BC: 12,16,20,... but single digits. B,C single digits: BC values div by 4: 12,16,20,24,28,32,...,96. With B,C≤9: 12,16,20,24,28,32,36,40,44,48,52,56,60,64,68,72,76,80,84,88,92,96. A=18−B−C. Try B=1,C=2: A=15 too big. B=4,C=8: A=6. 648: 6+4+8=18 , 48/4=12 . 648. B=7,C=2: A=9. 972: 9+7+2=18 , 72/4=18 . 972.

Q43. Students create and explore magic squares. 4 (i) Create a magic square with magic sum 24. Write all 9 entries.

Ans: Magic sum=24, centre=8. Entries 4 to 12 (Lo Shu+3): 7,12,5 / 6,8,10 / 11,4,9. Verify row

Q44. 7+12+5=24 (ii) What is the centre number of this magic square ?

Ans: No. Changing only the centre breaks the rows and diagonals through it. E.g. if centre becomes 9, the two diagonals now sum to 25, but rows through centre sum to 25, while rows not through centre still sum to 24. Not a magic square. Website: Click Here | Mob. : 8103405051 | WhatsApp: Click Here Page - 3 -