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Showing posts with label Cube roots of perfect cubes. Show all posts
Showing posts with label Cube roots of perfect cubes. Show all posts

Friday, November 27, 2015

Cube roots of perfect cubes

Here are eight poets, namely, A, B, C, D, E, F, G and H in respect of whom questions are being asked in the examination. The first four are ancient poets and the last four are modern poets. The question on ancient and modern poets is being asked in alternate years. Those who like H also like G, those who like D like C also. The examiner who sets question is not likely to ask question on D because he has written an article on him. But he likes D. Last year a question was asked on F. Considering these facts, on whom the question is most likely to be asked this year? 

a. B
b. C
c. D
d. G


Points to remember  for speedy  calculation of cube roots of perfect cubes

1. To calculate cube root of any perfect cube quickly, we need to remember the cubes of 1 to 10 which is given below.
=1
=8
=27
=64
=125
=216
7³ =343
=512
9³  =729
10³   =1000
2. From the above cubes of 1 to 10, we need to remember an interesting property.
=1=>If the last digit of the perfect cube = 1, the last digit of the cube root = 1
=8=>If the last digit of the perfect cube = 8, the last digit of the cube root = 2
=27=>If the last digit of the perfect cube = 7, the last digit of the cube root = 3
=64=>If the last digit of the perfect cube = 4, the last digit of the cube root = 4
=125=>If the last digit of the perfect cube =5, the last digit of the cube root = 5
=216=>If the last digit of the perfect cube = 6, the last digit of the cube root = 6
7³ =343=>If the last digit of the perfect cube = 3, the last digit of the cube root = 7
=512=>If the last digit of the perfect cube = 2, the last digit of the cube root = 8
9³  =729=>If the last digit of the perfect cube = 9, the last digit of the cube root = 9
10³   =1000=>If the last digit of the perfect cube = 0, the last digit of the cube root = 0