mình sẽ giải bài toán này theo 1 dm3 = 1lít nước nhé !

Thể tích của bể nước là : 4 x 3 x 2 = 24 ( m3 )

Phần thể tích bể chưa có nước có chiều cao là 0,2 m, chiều dài và chiều rông không thay dổi, vẫn là 4m và 3m.

Thể tích phần bể chưa có nước là : 4 x 3 x 0,2 = 2,4 ( m3 )

Phần thể tích bể có nước là : 24 - 2,4 = 21,6 ( m3 )

Đổi 21,6 m3 = 21600 dm3

1 phút cả hai vòi chảy vào bể được số lít nước là : 70 + 65 = 135 ( lít )

Số thời gian để cả hai vòi chảy đầy bể là : 21600 : 135 = 160 ( phút )

Đổi 160 phút = 2 giờ 40 phút

Người ta mở vòi lúc số giờ là : 10 giờ - 2giờ 40 phút = 7 giờ 20 phút

                                             Đáp số : 7 giờ 20 phút

Nhớ k cho mình nha các bạn !

cũng thế

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như thế nào

thông điệp nhỏ :

hãy tích khi ko muốn k

ai tích mình tích lại

Trong 1 giờ, vòi thứ nhất chảy được:

               1 : 2 = 1/2 (hồ)

Trong 1 giờ, vòi thứ hai chảy được:

               1 : 3 = 1/3 (hồ)

Trong 1 giờ, cả 2 vòi chảy được:

               1/2 + 1/3 = 5/6 (hồ)

Thời gian cả 2 vòi chảy đầy hồ là:

                1 : 5/6 = 6/5 (giờ)

Đổi: 6/5 giờ = 1,2 giờ = 1 giờ 12 phút

2 vòi chảy đầy hồ lúc:

                5 giờ 20 phút + 1 giờ 12 phút = 6 giờ 32 phút

                          Đáp số: 6 giờ 32 phút

6 gio 32phut