Joe's age,Joe's sister's age and Joe’s father's age sums up to a century . When son is as old as his father ,Joe's sister will be twice as old as now. When Joe is as old as his father then his father is twice as old as when his sister was as old as her father . Age of her father is?
Students attend our lectures, not because the mathematics we teach ‘makes lots of fun’ for us, but because they believe they can learn some essential knowledge from us. And each of our young students has only one life to live. We should therefore be a
H. Behnke
Mathematics is made of 50 percent formulas, 50 percent proofs, and 50 percent imagination.