Let P=51/5⋅251/25⋅1251/125⋅6251/625⋯
Then P can be expressed in the form ab/c, where a, b, and c are positive integers. Find the smallest possible value of a+b+c.
Simplify the following:
5^(1/5) 25^(1/25) 125^(1/125) 625^(1/625)
625^(1/625) = (5^4)^(1/625):
5^(1/5) 25^(1/25) 125^(1/125)×5^(4/625)
125^(1/125) = (5^3)^(1/125):
5^(1/5) 25^(1/25)×5^(3/125)×5^(4/625)
25^(1/25) = (5^2)^(1/25):
5^(1/5)×5^(2/25)×5^(3/125)×5^(4/625)
5^(1/5)×5^(2/25)×5^(3/125)×5^(4/625) = 5^(1/5 + 2/25 + 3/125 + 4/625):
5^(1/5 + 2/25 + 3/125 + 4/625)
Put 1/5 + 2/25 + 3/125 + 4/625 over the common denominator 625. 1/5 + 2/25 + 3/125 + 4/625 = 125/625 + (25×2)/625 + (5×3)/625 + 4/625:
5^(125/625 + (25×2)/625 + (5×3)/625 + 4/625)
25×2 = 50:
5^(125/625 + 50/625 + (5×3)/625 + 4/625)
5×3 = 15:
5^(125/625 + 50/625 + 15/625 + 4/625)
125/625 + 50/625 + 15/625 + 4/625 = (125 + 50 + 15 + 4)/625:
5^((125 + 50 + 15 + 4)/625)
125 + 50 + 15 + 4 = 194:
5^(194/625)
Thanks guests :)
P = 5^{1/5} \cdot 25^{1/25} \cdot 125^{1/125} \cdot 625^{1/625} \dotsm
P=51/5⋅251/25⋅1251/125⋅6251/625⋯P=51/5⋅52/52⋅53/53⋅54/54⋯P=5(15+252+353+454⋯)log5P=(15+252+353+454⋯)log5P=(15+152+153⋯)+(152+153+154⋯)+(153+154+155⋯)+…log5P=(15÷45)+(125÷45)+(1125÷45)+…log5P=(15×54)+(125×54)+(1125×54)+…log5P=(14)+(120)+(1100)+…log5P=14÷45log5P=14÷45log5P=14×54log5P=516P=5516P≈1.65359
LaTex
P = 5^{1/5} \cdot 25^{1/25} \cdot 125^{1/125} \cdot 625^{1/625} \dotsm\\
P = 5^{1/5} \cdot 5^{2/5^2} \cdot 5^{3/5^3} \cdot 5^{4/5^4} \dotsm\\
P = 5^{(\frac{1}{5}+\frac{2}{5^2}+\frac{3}{5^3}+\frac{4}{5^4}\dotsm\\)} \\
log_5 P = {(\frac{1}{5}+\frac{2}{5^2}+\frac{3}{5^3}+\frac{4}{5^4}\dotsm)} \\
log_5 P = {(\frac{1}{5}+\frac{1}{5^2}+\frac{1}{5^3}\dotsm)}
+ {(\frac{1}{5^2}+\frac{1}{5^3}+\frac{1}{5^4}\dotsm)}
+{(\frac{1}{5^3}+\frac{1}{5^4}+\frac{1}{5^5}\dotsm)+ \dots}\\
log_5 P =(\frac{1}{5}\div \frac{4}{5})+(\frac{1}{25}\div \frac{4}{5})+(\frac{1}{125}\div \frac{4}{5})+ \dots\\
log_5 P =(\frac{1}{5}\times \frac{5}{4})+(\frac{1}{25}\times\frac{5}{4})+(\frac{1}{125}\times\frac{5}{4})+ \dots\\
log_5 P =(\frac{1}{4})+(\frac{1}{20})+(\frac{1}{100})+ \dots\\
log_5 P =\frac{1}{4}\div \frac{4}{5}\\
log_5 P =\frac{1}{4}\div \frac{4}{5}\\
log_5 P =\frac{1}{4}\times \frac{5}{4}\\
log_5 P =\frac{5}{16}\\
P=5^{\frac{5}{16}}\\
P\approx 1.65359
Hi Melody:
When multiplied together, you get the following number:
(5^(1/5)) * (25^(1/25)) * (125^(1/125)) * (625^(1/625)) ==1.64801169512666976301802035295......etc.
1 - Guest #1 answer ==5^(4/13) ==1.64084551246609057805181222444......etc.
2 - Guest #2 answer==5^(194/625)==1.64801169512666976301802035295....etc.
3 - Melody's answer ==5^(5/16) ==1.65359110076253520866303943290......etc.