Exercise 3.3
Q1. Using divisibility test, determine which of the following numbers are divisible by 2; by 3; by 4; by 5; by 6; by 8; by 9; by 10; by 11. (Say yes or no)
Answer.
Number | Divisible by | ||||||||
2 | 3 | 4 | 5 | 6 | 8 | 9 | 10 | 11 | |
128 | Yes | No | Yes | No | No | Yes | No | No | No |
990 | Yes | Yes | No | Yes | Yes | No | Yes | Yes | Yes |
1586 | Yes | No | No | No | No | No | No | No | No |
275 | No | No | No | Yes | No | No | No | No | Yes |
6686 | Yes | No | No | No | No | No | No | No | No |
639210 | Yes | Yes | No | Yes | Yes | No | No | Yes | Yes |
429714 | Yes | Yes | No | No | Yes | No | Yes | No | No |
2856 | Yes | Yes | Yes | No | Yes | Yes | No | No | No |
3060 | Yes | Yes | Yes | Yes | Yes | No | Yes | Yes | No |
406839 | No | Yes | No | No | No | No | No | No | No |
Q2. Using divisibility test, determine which of the following numbers are divisibly by 4; by 8:
(a) 572
(b) 726352
(c) 5500
(d) 6000
(e) 12159
(f) 14560
(g) 21084
(h) 31795072
(i) 1700
(j) 2150
Answer.
(a) 572 ® Divisible by 4 as its last two digits are divisible by 4.
® Not divisible by 8 as its last three digits are not divisible by 8.
(b) 726352 ® Divisible by 4 as its last two digits are divisible by 4. ® Divisible by 8 as its last three digits are divisible by 8. (c) 5500 ® Divisible by 4 as its last two digits are divisible by 4. ® Not divisible by 8 as its last three digits are not divisible by 8. (d) 6000 ® Divisible by 4 as its last two digits are 0. ® Divisible by 8 as its last three digits are 0. (e) 12159 ® Not divisible by 4 and 8 as it is an odd number. (f) 14560 ® Divisible by 4 as its last two digits are divisible by 4. ® Divisible by 8 as its last three digits are divisible by 8. (g) 21084 ® Divisible by 4 as its last two digits are divisible by 4. ® Not divisible by 8 as its last three digits are not divisible by 8. (h) 31795072 ® Divisible by 4 as its last two digits are divisible by 4. ® Divisible by 8 as its last three digits are divisible by 8. (i) 1700 ® Divisible by 4 as its last two digits are 0. ® Not divisible by 8 as its last three digits are not divisible by 8. (j) 5500 ® Not divisible by 4 as its last two digits are not divisible by 4. ® Not divisible by 8 as its last three digits are not divisible by 8.
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