Calculate the MacCaulay Duration for a $1$ year fixed rate coupon bond paying $6$ % semiannually. You know that the yield of the bond is $6.72$ %.
$D_{mac}= \frac{\frac{(0.5)(1.5)}{1.0336}+\frac{(1)(1.5)}{1.0336^2}+\frac{(100}{1.0336^2}}{1.5 [\frac{1-(1.0336)^{-2}}{0.0336}]+\frac{100}{1.0336^2}}$
$D_{mac}=\frac{95.733808}{96.459}=0.9924$
But the answer is $0.9854$