Xiao Wang goes to work in the morning. Originally, he could arrive on time if he rode his bicycle at a speed of 15 km/h, but after riding for a while, he found that he had forgotten something at home. So he speeded up to 20 km/h, went home and got his things and went to work immediately. At this time, he was still 6 minutes late, but he found that if he used 25 km/h instead of 20 km/h, he could arrive on time. Then, how far did Xiao Wang ride and found that he forgot something?
小王早上去上班，本来他以15千米/时的车速骑车去的话刚好可以准时到，但是他骑了一会发现有东西忘在家里面了．于是他加快了速度到20千米/时，回家拿了东西马上又去上班．这时他还是迟到了6分钟，但是他发现当时要是不用20千米/时，而改用25千米/时，就可以准时到，那么请问，小王骑了多远发现忘了东西？
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