Answer :
Let the required year be x, then
1,400(1 + 0.013)^x = 850(1 + 0.04)^x
1400(1.013)^x = 850(1.04)^x
log(1400(1.013)^x) = log(850(1.04)^x)
log 1400 + log (1.013)^x = log 850 + log (1.04)^x
log 1400 + x log 1.013 = log 850 + x log 1.04
x log 1.04 - x log 1.013 = log 1400 - log 850
x(log 1.04 - log 1.013) = log 1400 - log 850
x = (log 1400 - log 850)/(log 1.04 - log 1.013) = 18.97 ≈ 19 years time.
Therefore, China will exceed US in the year 1995 + 19 = 2014.
1,400(1 + 0.013)^x = 850(1 + 0.04)^x
1400(1.013)^x = 850(1.04)^x
log(1400(1.013)^x) = log(850(1.04)^x)
log 1400 + log (1.013)^x = log 850 + log (1.04)^x
log 1400 + x log 1.013 = log 850 + x log 1.04
x log 1.04 - x log 1.013 = log 1400 - log 850
x(log 1.04 - log 1.013) = log 1400 - log 850
x = (log 1400 - log 850)/(log 1.04 - log 1.013) = 18.97 ≈ 19 years time.
Therefore, China will exceed US in the year 1995 + 19 = 2014.