Digital Delights

Wednesday 20th May

Activity one; to find the digital sum of a number, 

add it’s digits until you reach a single digit. 

Example; 43 has a digital sum of 4 + 3 =7 26 has a digital sum of 2 + 6 = 8

A. Find the digital sum of these numbers:

18 (1 + 8 = 9)  

27 (2 + 7 = 9)  

36 (3 + 6 = 9)

45 (4 + 5 = 9)

54 (5 + 4 = 9)

63 (6 + 3 = 9) 

72 (7 + 2 = 9)  

81 (8 + 1 = 9)

B. What do you see? That some of the numbers are the same as the others

C. What do these numbers have in common? They all add up to 9

Sometimes you need to add digits more than once to reach a single digit. Example; 98 9 + 8 = 17 ----> 1 + 7 = 8

74 (7+ 4 =11) ----> (1 + 1 = 2)

59 (5+9=14) ----> (1 + 4 = 5)

Activity Two; The multiples of eight are the 

answer to the eight times table 

Multiples of 8;      8        16        24        32       40     48    56    64    72    88         Digital sum;         8        7          6         5         4       12      11     10    9      16

Multiples of 7;     7     14     21     28     35     42     49     56     63     70     77  Digital sum;        7      5       3      10      8      6       13      11      9       7     14

Multiples of 6;     6     12     18     24     30    36     42     48     54     60     66       Digital sum;        6      3       9      6       3      9       7      12      9         6      12

Multiples of 5;     5     10     15     20     25    30     35     40     45     50     55       Digital sum;        5      1       6       2       7      3       8       4       9       5      10