Câu 1: Tính nhanh: a/ \(\dfrac{3}{11x12}\)+\(\dfrac{3}{12x13}\)+\(\dfrac{3}{13x14}\)+\(\dfrac{3}{14x15}\)
b/\(\dfrac{2}{2X3}\)+\(\dfrac{2}{3x4}\)+\(\dfrac{2}{4x5}\)+\(\dfrac{2}{5x6}\)
c/ \(\dfrac{3}{1x4}\)+\(\dfrac{3}{4x7}\)+\(\dfrac{3}{7x10}\)+................+\(\dfrac{3}{97x100}\)
d/ \(\dfrac{3}{2x5}\)+\(\dfrac{3}{5x8}\)+\(\dfrac{3}{8x11}\)+.............+\(\dfrac{3}{100x103}\)
e/ \(\dfrac{1}{1x5}\)+\(\dfrac{1}{5x10}\)+\(\dfrac{1}{10x15}\)+..................+\(\dfrac{1}{95x100}\)
Toán lớp 5 nha, giúp với mai mình học r, đúng mk tick cho.