[ 2 7 ° ] 
<{ fhould happen before the death of B, aged like- 
“ wife 40. What fnm fhould now be advanced to 
t! him for fuch a reverfion, intereft being reckoned 
“ at 4 per cent. ?” 
In lolving this problem, agreeably to the method 
juft defcribed; we are to find the value of 40/. per 
ann. to be entered upon certainly at the death of A, 
and then to multiply this value by the chance that A 
fhall not furvive B, or by I; and in this way the anfwer 
comes out the fame as that already given. Now, 
it may be eafily feen that this muft be wrong. The- 
value of a reverfion to be received when a perfon 
of a given age dies, cannot be the fame whether the 
condition of obtaining it is, that he fliall die before , , 
or that he (hall die after another perfon; that is, 
whether it is provided that a purchafer, if he fucceeds, 
fhall get into pofleffion fooner or later. The reverfion 
in the latter cafe muft, without doubt, be of lefs value 
than in the former. 
The firft queftion here propofed refolves itfelf into 
the following general queftion. “ What is the pre- 
“ fent value of a given reverfionary fum or eftate, to 
“ be received after the failure of two lives, provided 
“ one in particular of them fhould be the longeft: 
“ life?” 
Now, the prefent value of an eftate to be en- 
joyed for ever after the failure of the longeft of 
two lives, is the value of the longeft of the two 
lives fubtradted from the perpetuity. The value 
of the longeft of two lives is, it is well known, 
the value of the two joint lives fubtradled from the 
fum of the values of the two fingle lives. In the 
prelent cafe, therefore, it is 9.82 (the value of two 
