Bank Math Master১টি পরীক্ষায় এসেছেপ্রশ্ন ৬Ratul covers half of his journey at 3 km/h and the remaining half at 6 km/h. His average speed is-কক) 4 kmphখখ) 4.5 kmphগগ) 5 kmphঘঘ) 5.5 kmphউত্তর দেখুন