Autoroad builders do 4 km of the road in a week. Kogda length of the road reached 76 km, the constructed part of the road began to be marked. In how many weeks markers dogonya autoroad builders if the speed of autoroad builders is 2/21 speeds of markers

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1) Va = 4 km/week ⇒ Va = 2/21 × Vp = 4 Vp = 4: 2/21 = 4/1 * 21/2 = 2*21 = 42 (km/week) the speed of the Task markers 2) on the movement "after " ⇒ Vsbl. = Vp - Va Vsbl. = 42 - 4 = 38 (km/week) speed of rapprochement of markers and autoroad builders 3) t = S ÷ Vsbl. t = 76÷38 = 2 (weeks) time which will be required to markers to catch up with autoroad builders. Let's check: 76 + 4×2 + 76 = 84 (km) distance which autoroad builders 42 × 2 = will make 84 (km) distance which markers of 84 km = will mark 84 km ⇒ markers caught up with Answer's autoroad builders: in 2 weeks the markers will catch up with autoroad builders.
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