# Aptitude - Surds and Indices - Discussion

### Discussion :: Surds and Indices - General Questions (Q.No.4)

4.

If 5a = 3125, then the value of 5(a - 3) is:

 [A]. 25 [B]. 125 [C]. 625 [D]. 1625

Explanation:

5a = 3125 5a = 55 a = 5. 5(a - 3) = 5(5 - 3) = 52 = 25.

 Girish said: (Jun 18, 2011) Also 5a-3 = 5a/53 = 3125/125 = 25

 Girish said: (Jun 18, 2011) Above can be read as 5^a-3 = 5^a/5^3 = 3125/125 = 25

 Shridhar Naik said: (Sep 16, 2012) 5^(a-3)=5^a*5^(-3)=3125/125=25

 Bisu said: (May 27, 2013) Also can be solved. 5^a = 3125. 5^(a-3) = ? ==>5^(a-3) = 5^a/5^3 = 3125/125 = 25.

 Veronika said: (Jan 11, 2017) I am very new to this, what does ^ mean? I really need help.

 Swapnil said: (Jan 12, 2017) 5 a-3 = 5^a/5^3. = 3125/125. = 25.

 Shalini said: (Apr 27, 2017) @Veronika: ^ means raise to the power, i.e. 5^a= 5 raise to the power a.

 Ayesha said: (May 9, 2017) Why in the question they have to ask 5a they should have directly written it as 5^a did they get the same meaning? Please, someone tell me.

 Babu Vijayendra Kumar said: (Jun 26, 2017) I'm not getting this, anybody explain the logic.

 Aditya said: (Jul 22, 2017) 5a=3125 we can write 3125 in 5 * 5 * 5 * 5 * 5 then we get 5 power 5 then put value. Then, we get 5 power 2 we get 25.

 Ramesha T S said: (Oct 15, 2017) 5^(a-3)=(5^a)/(5^3)=3125/(5*5*5) = 25.

 Mandeep Mehra said: (Sep 15, 2018) 5^a=3125. 5^a-3=5^a/5^3. 5^a/5^3=3125/125=25.

 Asra said: (Apr 13, 2019) How to get the value of a by 5^a= 3125? Someone please help.

 Dhika said: (May 15, 2019) Here, the value of 5^a=3125.

 Urvashi said: (Jul 22, 2020) Given that 5^a = 3125 5^a = (5*5*5*5*5) Since (5*5*5*5*5) = 3125. So, 5 power a = 5 power 5. Since bases are same! Then subtract 3 from each according to question! 5^(a-3) = 5^(5-3), 5^(a-3) = 5^2, 5^(a-3) = (5*5). 5^(a-3) = 25.

 Siddharth Sahu said: (Jul 24, 2021) The simple method is 5^a/5^3 = 3125/5^3. That is equal to 5^a-3=3125/125 = 25.