Tính:
a) 683 \(\times\) 35; 1954 \(\times\) 425; 2438 \(\times\) 306.
b) \(\dfrac{7}{9}\times\dfrac{3}{35}\); \(\dfrac{9}{22}\times\) 55; \(\dfrac{11}{17}:\dfrac{33}{34}\).
c) 36,66 \(:\) 7,8; 15,7 \(:\) 6,28; 27,63 \(:\) 0,45.
d) 16 giờ 15 phút \(:\) 5; 14 phút 36 giây \(:\) 12.