Sunday, June 10, 2018

Problem: Simplify (33076161)^⅓ + (279841)^¼ + (243)^⅕ = ?

(33076161)^1/3 + (279841)^1/4 + (243)^1/5 = ?
Given options are
  • 344
  • 345
  • 346
  • 347
  • None of these

The solution involves in four steps
  • Finding the cube root of the number 33076161
  • Finding the fourth root of 279841
  • Find the fifth root of 243
  • Adding all the three numbers

  1. Finding the cube root of the number 33076161

TP   SP   FP - We will be finding the numbers in these three places as below.

  • Divide the number in three parts
    • First number (FN)   : 33
    • Second number (SN) : 076
    • Third number (TN) : 161

To find the cube root, we will use TN, then FN and finally SN.

  • TN ends with 1, so the number in the ones place (FP) is 1. (Refer Table 1 below)
TP   SP   1
  • FN is 33, which in between the cube of 3 and 4, so we have to choose the small number which is 3 will be in third place (TP). (Refer table 1 below)
3  SP  1
  • To find the number in second place, we can use the formula - 3*(TP^2)*SP= second digit of (TN-FP)
    • 3*(1^2)*SP= Second digit of (161-1) = Second digit of 160 = 6
    • 3*(1^2)*SP=6
    • SP=6/3=2
3  2  1
  • Finally, cube root of (33076161)⅓ is 321


2. Finding the fourth root of 279841
    • First find the square  root of the number 279841
    • Square root of 279841 is 529
    • Again find the square root of 529
    • Square root of 529 is 23
    • (23^4)¼=23

3. Find the fifth root of 243
    • Rewrite 243 as 3^5
    • Cancel the common factor of 5
    • And the answer is 3

4. Then, the final step is adding all the three numbers 321+23+3=347

Table 1: Square, Cube, Numbers Ranging 0 - 10

Number x
Square x2
Cube x3
1
1
1
2
4
8
3
9
27
4
16
64
5
25
125
6
36
216
7
49
343
8
64
512
9
81
729
10
100
1000

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