Tom asked his Granny how old she was Rather than giving him a
straight answer,she replied, "i have 6 children, and there are 4
years between each one and the next, i had my first child (Your
uncle peter) When i was 19. Now the youngest one (Your aunty
jane) is 19 herself, Thats all i'm telling you.How old is tom's Granny?

58

Spot On !!!

aaidel: 58

@OP, BTW when you say 4 years in between each one, it might not necessarily mean 4 years older, for brevity sake.

The ansa is 63

Last Child - 19
5th Child - 23
4th Child - 27
3rd Child - 31
2nd Child - 35
1st Child - 39
Granny = 19 + 39 = 58

zz

// fields
numOfch = 6 //number of children
ageDiff = 4
gAgeFc = 19 //grannie age at first child
ageYcNw = 19 // now age of youngest child.
grannyAgeNow=??//yet 2 b determined
//Functions:

/*cumulative age difference*/

cumAgeDiff(AgeDifference,numOfChildren)
{
return ageDifference*numOfChildren-1
}

/*grannies age after nth child */

gAgeAtNthCh(nthChild,grannyAgeFirstChild)
{
return grannyAgeFirstChild+cumAgeDiff(ageDiff,nthChild)
}

/* grannies age now */

gAgeNow(grannyAgeNthChild, nowAgeNthChild)
{
if(nowAgeNthChild<0)
return -1
return grannyAgeNthChild+nowAgeNthChild
}

//grannys age at 6th child

grannyAgeNow = gAgeNow(gAgeNthCh(6,19), 19)

//or

grannyAgeNow = gAgeNow(gAgeNthCh(numOfCh,gAgeFc), ageYcNw).

//gAgeNow=58