EXPONENT RULES

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cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pm; Thanked: 331 times; Followed by:11 members

EXPONENT RULES

by cramya » Sat Oct 25, 2008 8:07 pm

Confirmation needed please:

Rule 1: (a^b)^c = a^(b*c)

Rule2: a^b^c without any parentheses

We calculate b^c first and then raise it to a^(calculated value of b^c)

The reason I am asking this is because I got a gmat prep question that read:

2^(4-1)^2

I calculated it as 2^6 but the correct answer was

[spoiler] 2 ^ 8 [/spoiler]

Feedback appreciated!

Quote

Source: Beat The GMAT — Problem Solving | Sat Oct 25, 2008 8:07 pm

cramya: Legendary Member; Posts: 2467; Joined: Thu Aug 28, 2008 6:14 pm; Thanked: 331 times; Followed by:11 members

by cramya » Sat Oct 25, 2008 8:09 pm

Correction to the OA inside the SPOILER:

Confirmation needed please:

Rule 1: (a^b)^c = a^(b*c)

Rule2: a^b^c without any parentheses

We calculate b^c first and then raise it to a^(calculated value of b^c)

The reason I am asking this is because I got a gmat prep question that read:

2^(4-1)^2

I calculated it as 2^6 but the correct answer was

[spoiler]2 ^ 9 [/spoiler]

Feedback appreciated!

Quote

Mani_mba: Master | Next Rank: 500 Posts; Posts: 267; Joined: Wed Jul 16, 2008 12:20 am; Thanked: 4 times; Followed by:1 members

by Mani_mba » Sat Oct 25, 2008 8:51 pm

I think your rules are correct. But you applied it wrongly.

In this particular question, Your Rule 2 needs to be applied.

2 ^ (4-1)^2
=> 2^3^2

=> 2^9.

Quote

sudhir3127: Legendary Member; Posts: 829; Joined: Mon Jul 07, 2008 10:09 pm; Location: INDIA; Thanked: 84 times; Followed by:3 members

Re: EXPONENT RULES

by sudhir3127 » Sat Oct 25, 2008 9:07 pm

cramya wrote:Confirmation needed please:

Rule 1: (a^b)^c = a^(b*c)

Rule2: a^b^c without any parentheses

We calculate b^c first and then raise it to a^(calculated value of b^c)

The reason I am asking this is because I got a gmat prep question that read:

2^(4-1)^2

I calculated it as 2^6 but the correct answer was

[spoiler] 2 ^ 8 [/spoiler]

Feedback appreciated!

Hi ramya
Just as Mani said... ur Rules are right but the application is a bit off..

2^(4-1)^2
= a^(b)^c.. in this case we need to first solve the b^c
= 3^2 = 9
thus its 2^9

had it been
(2^4-1)^2
(2^3)^2 then its (a^b)^c = a^bc
thus its 2^3*2 = 2^6..

hope it makes sense.. do let me know if u need any more clarification the above rule...