FINDING CUBE OF NUMBERS
Students should remember cubes of 10 numbers.
13 = 1
23 = 8
33 = 27
43 = 64
53 = 125
63 = 216
73 = 343
83 = 512
93 = 729
103 = 1000
We take an example and understand this method.
Let us find the cube of 13 –First write two digits of 13 in the first 2 places Write square of 2nd digit (here 3) in the third place and cube of 2nd digit in the fourth place
1 3 9 27
Double the middle numbers and add
1 3 9 27
6 18
(1) (2) (2)
2 1 9 7
∴ 133 = 2197
We see another example
Let us find the cube of 15 – Square of 5 = 25; cube of 5 = 125
1 5 25 125
Double the middle numbers and add
1 5 25 125
10 50
(2) (8) (12)
3 3 7 5
∴ 153 = 2197
Similarly,Cube of 18 -1 8 64 512 Double the middle numbers and add
1 8 64 512
16 128
(4) (24) (51)
5 8 3 2
∴ 183 = 5832
TRY THESE
1. 143 2. 123 3. 173 4. 163 5. 193
KEY
1. 2744 2. 1728 3. 4913 4. 4096 5. 6859