Posted on: Thu, 2008-07-17 08:18
Incognito
tens digit
The Tens digit of (1875)51 x (23)23 equals
a. 9
b. 7
c. 5
d. 3
e. 2
n/a
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ans is 7
if odd power of 1875 then tens digit=7
if even power of 1875 then tens digit=2
Little Star
n/a
(1875)51 * (23)23
To find: Tens digit of 7551*2323
even power of 75 => 25
odd power of 75 => 75 as last two digits. ................ Equation 1
now (23)2 = 529 => 29
then (23)4 = (29)2 = 841 => 41
then (23)8 = (41)2 = 1681 => 81
then (23)16 = (81)2 = 6561 => 61
then (23)20 = 2316*234 = 61*41 = 2501 => 01
then (23)22 = 2320*232 = 01*29 =======> 29
then (23)23 = 2322*231 = 29*23 = 667 ==> 67 ................ Equation 2
From Equations 1 & 2,
7551*2323 = 75*67 = 5025 => 25
Hence the ten's digit is 2. Option (e) is correct.
n/a
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