Реши : в 1 день турист всего маршрута, во 2- 1/3 маршрута. какую часть всего маршрута ему осталось пройти

Приводить к общему знаменателю и получаем 6/24+8/24=14/24 Сокращаем и получаем 7/12

Пусть Х---скорость первого байкера

тогда Х-16---скорость второго байкера на первой половине пути

путь они проехали один и тот же S

время потратили одинаковое:

время первого байкера S/X

время второго байкера S/(2*(X-16)) + S/(2*120)

получим уравнение

S/X = S/(2*(X-16)) + S/(2*120)

1/X = 1/(2*(X-16)) + 1/(2*120)

2/X - 1/(X-16) = 1/120

(2*(X-16) - Х) / (Х*(X-16)) = 1/120

120*(X-32) = Х*(X-16)

120*X - 120*32 - Х*X + 16*Х = 0

Х*X - 136*X + 120*32= 0

D = 136*136 - 4*120*32 = 8*17*8*17 - 4*2*60*8*4 = 8*8*(17*17 - 60*4) = 8*8*(289-240) = 8*8*49

X1 = (136 + 8*7)/2 = 68 + 4*7 = 96

X2 = (136 - 8*7)/2 = 68 - 4*7 = 40---не удовлетворяет условию

ответ: скорость первого байкера 96 км/час

ПРОВЕРКА:

время в пути первого байкера S/96

время в пути второго байкера S/2 : (96-16) + S/2 : 120 = S/(2*80) + S/(2*120) = S/160 + S/240 = (3S+2S)/480 = 5S/480 = S/96

т.е. они доехали одновременно

1)1.7-14=-7                                                                                                                                                         2.-28:-7=4                                                                                                                                                            3.4-10=-6                                                                                                                                                            задача а: 36*2/9=8 лет                                                                                                                                    задача б: 5:4*100=125%                                                                                                                                задача в 40%=20 слов                           40%=0,4                                                                                         20:0,4=50 слов                                                                                                                                                  10(1-0,2у)-(1-у)=17                                                                                                                                            10-2у-1+у=17                                                                                                                                                      9-у=17                                                                                                                                                                   у=9-17=-8                                                                                                                                                            щас остальные ответы напишу                                                                                                               задача:60 + 8=68км/час - второй поезд                                                                                               24*1/3=8 часов-ехали поезда                                                                                                                 60*8+68*8=1004 км                                                                                                                                   задача:72-12=60м-стала длина забора                                                                                              26-7=19м-стала ширина забора                                                                                                            60*19=1140 м2