Mathematics for IGCSE & O level - Proportion (Section 1 - No. 10)
If *a* is directly proportional to *b* and *a* is 10 when *b* is 2, what is the value of *a* when *b* = 5?
4
10
25
50
Giải thích
a = kb; 10= k*2; k=5; so a =5b; Therefore if b is 5, a is 25.