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this is very easy math .i can solve this math .answer is 13km/hr

nice and genius question.very good dear

excellent post.i like your post.this is Mathematical question.carry no dear.thanks for youe post

if you solve this math you must know that about what is actual speed and effective speed.

downstream,upstream,actual speed,effective speed are more important for this math.

good post.i can solve this problem.this is very easy math.the final answer is 13.am i right dear

your answer are absolutely right.thanks for your comment dear.