Study the pattern:
1× 8 + 1 = 9
12 × 8 + 2 = 98
123 × 8 + 3 = 987
1234 × 8 + 4 = 9876
12345 × 8 + 5 = 98765
Write the next two steps. Can you say how the pattern works?
From the given pattern, the 1st step is: 1× 8 + 1 = 9
And the 2nd step: 12 × 8 + 2 = 98, which can be written as :
(11 + 1) × 8 + 2
On following distributive property, we get,
= (11 × 8) + (1 × 8) + 2
= 88 + 8 + 2 = 98
Therefore, we can write the 3rd step: 123 × 8 + 3 = 987 as,
= (111 + 11 + 1) × 8 + 3
= 111 × 8 + 11 × 8 + 1 × 8 + 2
= 888 + 88 + 8 + 3 = 987
Similarly, 4th step: 1234 × 8 + 4 = 9876 as,
= (1111 + 111 + 11 + 1) × 8 + 4
= 1111 × 8 + 111 × 8 + 11× 8 + 1 × 8 + 4
= 8888 + 888 + 88 + 8 + 4 = 9876
In the same way, the next steps are:
5th step: 12345 × 8 + 5, can be written as,
= (111111 + 11111 + 1111 + 111 + 11 + 1) × 8 + 5
= 111111 × 8 + 11111 × 8 + 1111 × 8 + 111× 8 + 11 × 8 + 1 × 8 + 5
= 888888 + 88888 + 8888 + 888 + 88 + 8 + 6 = 98765
Thus, the 5th term is : 12345 × 8 + 5 = 98765
Now, the 6th step: 123456 × 8 + 6 can be written as,
= (1111111 + 111111 + 11111 + 1111 + 111 + 11 + 1) × 8 + 7
= 1111111 × 8 + 111111 × 8 + 11111 × 8 + 1111 × 8 + 111× 8 + 11 × 8 + 1 × 8 + 7
= 8888888 + 888888 + 88888 + 8888 + 888 + 88 + 8 + 7
= 9876543
Thus, the 6th step is: 123456 × 8 + 6 = 9876543